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add 311 java
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‎README.md‎

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@@ -240,7 +240,7 @@
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289| [Game of Life](https://leetcode.com/problems/game-of-life/) | [Python](./leetcode_python/Array/game-of-life.py) | _O(m * n)_ | _O(1)_ | Medium |simultaneous,matrix,`complex`, `google`, `amazon`| AGAIN*** (4)
241241
293| [Flip Game](https://leetcode.com/problems/flip-game/) | [Python](./leetcode_python/Array/flip-game.py) | _O(n * (c+1))_ | _O(1)_ | Easy |🔒, `basic`| AGAIN*
242242
308| [Range Sum Query 2D - Mutable](https://leetcode.com/problems/range-sum-query-2d-mutable/) | [Python](./leetcode_python/Array/range-sum-query-2d-mutable.py) | _O(n * (c+1))_ | _O(1)_ | Hard |LC 303, pre-sum, matrix, tree, 🔒, `google`| not start
243-
311| [Sparse Matrix Multiplication](https://leetcode.com/problems/sparse-matrix-multiplication/) | [Python](./leetcode_python/Array/sparse-matrix-multiplication.py) | _O(m * n * l)_ | _O(m * l)_ | Medium |🔒, matrix, `basic`, `fb`| OK**** (4)
243+
311| [Sparse Matrix Multiplication](https://leetcode.com/problems/sparse-matrix-multiplication/) | [Python](./leetcode_python/Array/sparse-matrix-multiplication.py), [Java](./leetcode_java/src/main/java/LeetCodeJava/Array/SparseMatrixMultiplication.java)| _O(m * n * l)_ | _O(m * l)_ | Medium |🔒, matrix, `basic`, `fb`,google| OK**** (5)
244244
334| [Increasing Triplet Subsequence](https://leetcode.com/problems/increasing-triplet-subsequence/) | [Python](./leetcode_python/Array/increasing-triplet-subsequence.py), [Java](./leetcode_java/src/main/java/LeetCodeJava/Array/IncreasingTripletSubsequence.java) | _O(n)_ | _O(1)_ | Medium |AGAIN, check `# 300 Longest Increasing Subsequence`, `trick`, `fb`, google|OK***** (but again) (4)
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370| [Range Addition](https://leetcode.com/problems/range-addition/) | [Python](./leetcode_python/Array/range-addition.py), [Java](./leetcode_java/src/main/java/LeetCodeJava/Array/RangeAddition.java) | _O(k + n)_ | _O(1)_ | Medium |prefix, diff array, check `# 598 Range Addition II`, `amazon`, LC 1109, google| AGAIN************** (4) (MUST)
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384| [Shuffle an Array](https://leetcode.com/problems/shuffle-an-array/) | [Python](./leetcode_python/Array/shuffle-an-array.py) | _O(n)_ | _O(n)_ | Medium | EPI, `trick` | OK*

‎data/progress.txt‎

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20241222: 369
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20241222: 369,311
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20241221: 370
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20241220: 815,871,593,1109
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20241214: 560,523

‎data/to_review.txt‎

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2025-02-15 -> ['369']
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2025-02-15 -> ['369,311']
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2025-02-14 -> ['370']
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2025-02-13 -> ['815,871,593,1109']
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2025-02-07 -> ['560,523']
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2025-02-01 -> ['304,853,325']
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2025-01-26 -> ['370(todo)']
7-
2025-01-25 -> ['369']
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2025-01-25 -> ['369,311']
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2025-01-24 -> ['370', '34,767']
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2025-01-23 -> ['815,871,593,1109']
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2025-01-20 -> ['722,380']
@@ -13,21 +13,21 @@
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2025-01-16 -> ['776,31']
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2025-01-15 -> ['004(todo),34(todo),162(todo),275(todo)']
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2025-01-14 -> ['986(todo),1229(todo),1868(todo),80(todo),209(todo),283(todo),360(todo),713(todo),532(todo),611(todo)']
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2025-01-12 -> ['369']
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2025-01-12 -> ['369,311']
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2025-01-11 -> ['370', '304,853,325', '394']
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2025-01-10 -> ['815,871,593,1109', '833,950']
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2025-01-05 -> ['370(todo)']
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2025-01-04 -> ['369', '560,523', '53,210,207']
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2025-01-04 -> ['369,311', '560,523', '53,210,207']
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2025-01-03 -> ['370', '34,767', '444']
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2025-01-02 -> ['815,871,593,1109', '1188,130,855(again)']
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2024-12-30 -> ['369', '722,380']
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2024-12-30 -> ['369,311', '722,380']
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2024-12-29 -> ['370', '304,853,325', '33,81']
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2024-12-28 -> ['815,871,593,1109', '900']
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2024-12-27 -> ['369', '560,523', '253', '26,27', '802,1197,26']
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2024-12-27 -> ['369,311', '560,523', '253', '26,27', '802,1197,26']
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2024-12-26 -> ['370', '776,31']
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2024-12-25 -> ['369', '815,871,593,1109', '004(todo),34(todo),162(todo),275(todo)']
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2024-12-24 -> ['369', '370', '986(todo),1229(todo),1868(todo),80(todo),209(todo),283(todo),360(todo),713(todo),532(todo),611(todo)']
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2024-12-23 -> ['369', '370', '815,871,593,1109', '370(todo)']
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2024-12-25 -> ['369,311', '815,871,593,1109', '004(todo),34(todo),162(todo),275(todo)']
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2024-12-24 -> ['369,311', '370', '986(todo),1229(todo),1868(todo),80(todo),209(todo),283(todo),360(todo),713(todo),532(todo),611(todo)']
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2024-12-23 -> ['369,311', '370', '815,871,593,1109', '370(todo)']
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2024-12-22 -> ['370', '815,871,593,1109', '560,523']
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2024-12-21 -> ['815,871,593,1109', '304,853,325', '34,767', '394', '855,846']
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2024-12-20 -> ['833,950', '932']

‎leetcode_java/src/main/java/LeetCodeJava/Array/SparseMatrixMultiplication.java‎

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package LeetCodeJava.Array;
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// https://leetcode.com/problems/sparse-matrix-multiplication/description/
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// https://leetcode.ca/all/311.html
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import java.util.ArrayList;
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import java.util.Arrays;
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import java.util.List;
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/**
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* 311. Sparse Matrix Multiplication
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* Given two sparse matrices A and B, return the result of AB.
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*
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* You may assume that A's column number is equal to B's row number.
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*
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* Example:
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*
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* Input:
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*
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* A = [
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* [ 1, 0, 0],
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* [-1, 0, 3]
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* ]
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*
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* B = [
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* [ 7, 0, 0 ],
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* [ 0, 0, 0 ],
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* [ 0, 0, 1 ]
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* ]
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*
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* Output:
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*
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* | 1 0 0 | | 7 0 0 | | 7 0 0 |
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* AB = | -1 0 3 | x | 0 0 0 | = | -7 0 3 |
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* | 0 0 1 |
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* Difficulty:
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* Medium
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* Lock:
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* Prime
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* Company:
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* Amazon Apple Bloomberg Facebook Goldman Sachs Google LinkedIn Microsoft Snapchat
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*
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*/
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public class SparseMatrixMultiplication {
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// V0
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// IDEA : ARRAY OP (fix by gpt)
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/**
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* Why there is 3 loop ?
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*
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* -> Matrix Multiplication: Ci,j = Sigma(Aik * Bkj)
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*
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* -> so we have 3 layer loop as below:
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* - i : Iterates over the rows of A (outer loop).
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* - j : Iterates over the columns of B (second loop).
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* - k : Iterates over the “shared dimension” (columns of A or rows of B ) to compute the dot product (inner loop).
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*
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*
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* ->
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*
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* The Role of the Loops
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* 1. Outer loop ( i ): Iterates over the rows of mat1 to calculate each row of the result matrix.
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* 2. Middle loop ( j ): Iterates over the columns of mat2 to compute each element in a row of the result matrix.
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* 3. Inner loop ( k ): Iterates over the “shared dimension” to compute the dot product of the i^{th} row of mat1 and the j^{th} column of mat2.
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*
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*
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* -> Why the Inner Loop ( k ) Exists ?
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*
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* -> The inner loop is necessary
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* because each element of the result matrix
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* is computed as the dot product of a
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* row from mat1 and a column from mat2.
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* Without this loop, the computation of the dot product would be incomplete.
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*/
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public static int[][] multiply(int[][] mat1, int[][] mat2) {
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// Edge case: Single element matrices
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if (mat1.length == 1 && mat1[0].length == 1 && mat2.length == 1 && mat2[0].length == 1) {
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return new int[][]{{mat1[0][0] * mat2[0][0]}};
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}
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int l_1 = mat1.length; // Number of rows in mat1
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int w_1 = mat1[0].length; // Number of columns in mat1 (and rows in mat2)
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int w_2 = mat2[0].length; // Number of columns in mat2
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// Initialize the result matrix
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int[][] res = new int[l_1][w_2];
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// Perform matrix multiplication
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for (int i = 0; i < l_1; i++) {
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for (int j = 0; j < w_2; j++) {
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int sum = 0; // Sum for res[i][j]
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for (int k = 0; k < w_1; k++) {
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sum += mat1[i][k] * mat2[k][j];
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}
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res[i][j] = sum;
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}
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}
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return res;
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}
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// V1
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// IDEA : ARRAY OP (gpt)
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public int[][] multiply_1(int[][] A, int[][] B) {
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int m = A.length; // Number of rows in A
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int n = A[0].length; // Number of columns in A
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int p = B[0].length; // Number of columns in B
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int[][] result = new int[m][p];
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// Iterate through rows of A
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for (int i = 0; i < m; i++) {
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for (int k = 0; k < n; k++) {
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if (A[i][k] != 0) { // Skip zero entries in A
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for (int j = 0; j < p; j++) {
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if (B[k][j] != 0) { // Skip zero entries in B
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result[i][j] += A[i][k] * B[k][j];
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}
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}
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}
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}
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}
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return result;
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}
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// V2
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// https://leetcode.ca/2016-10-06-311-Sparse-Matrix-Multiplication/
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public int[][] multiply_2(int[][] mat1, int[][] mat2) {
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int m = mat1.length, n = mat2[0].length;
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int[][] ans = new int[m][n];
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List<int[]>[] g1 = f(mat1);
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List<int[]>[] g2 = f(mat2);
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for (int i = 0; i < m; ++i) {
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for (int[] p : g1[i]) {
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int k = p[0], x = p[1];
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for (int[] q : g2[k]) {
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int j = q[0], y = q[1];
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ans[i][j] += x * y;
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}
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}
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}
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return ans;
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}
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private List<int[]>[] f(int[][] mat) {
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int m = mat.length, n = mat[0].length;
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List<int[]>[] g = new List[m];
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Arrays.setAll(g, i -> new ArrayList<>());
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for (int i = 0; i < m; ++i) {
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for (int j = 0; j < n; ++j) {
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if (mat[i][j] != 0) {
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g[i].add(new int[] {j, mat[i][j]});
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}
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}
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}
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return g;
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}
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// V3
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}

‎leetcode_java/src/main/java/dev/workspace6.java‎

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@@ -515,32 +515,89 @@ public ListNode plusOne(ListNode head) {
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return null;
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}
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// v1
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// public ListNode plusOne_1(ListNode head) {
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// if (head == null){
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// return new ListNode(1); // ??
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// }
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// List<Integer> list = new ArrayList<>();
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// while(head != null){
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// list.add(head.val);
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// head = head.next;
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// }
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// // ???
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// int cur = 0;
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// for (int j = list.size(); j >= 0; j--){
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// cur += (10 ^ j) * list.get(j);
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// }
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// cur += 1;
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// ListNode res = new ListNode();
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// String string = String.valueOf(cur);
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// for (String x : string.split("")){
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// ListNode tmp = new ListNode();
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// tmp.val = Integer.parseInt(x);
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// res.next = tmp;
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// res = res.next;
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// }
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//
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// return res;
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// }
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// v1
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// public ListNode plusOne_1(ListNode head) {
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// if (head == null){
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// return new ListNode(1); // ??
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// }
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// List<Integer> list = new ArrayList<>();
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// while(head != null){
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// list.add(head.val);
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// head = head.next;
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// }
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// // ???
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// int cur = 0;
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// for (int j = list.size(); j >= 0; j--){
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// cur += (10 ^ j) * list.get(j);
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// }
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// cur += 1;
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// ListNode res = new ListNode();
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// String string = String.valueOf(cur);
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// for (String x : string.split("")){
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// ListNode tmp = new ListNode();
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// tmp.val = Integer.parseInt(x);
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// res.next = tmp;
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// res = res.next;
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// }
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//
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// return res;
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// }
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// LC 311
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// https://leetcode.ca/2016-10-06-311-Sparse-Matrix-Multiplication/
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// 4.39 - 4.50 pm
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/**
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* IDEA 1: ARRAY OP (brute force)
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*
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* Input:
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*
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* A = [
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* [ 1, 0, 0],
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* [-1, 0, 3]
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* ]
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*
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* B = [
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* [ 7, 0, 0 ],
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* [ 0, 0, 0 ],
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* [ 0, 0, 1 ]
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* ]
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*
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* Output:
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*
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* | 1 0 0 | | 7 0 0 | | 7 0 0 |
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* AB = | -1 0 3 | x | 0 0 0 | = | -7 0 3 |
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* | 0 0 1 |
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*
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*/
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public int[][] multiply(int[][] mat1, int[][] mat2) {
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// edge case
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if (mat1.length == 1 && mat1[0].length == 1 && mat2.length == 1 && mat2[0].length == 1){
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int[][] res = new int[][]{};
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res[0][0] = mat1[0][0] * mat2[0][0];
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return res;
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}
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int l_1 = mat1.length;
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int w_1 = mat1[0].length;
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int l_2 = mat2.length;
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int w_2 = mat2[0].length;
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int[][] res = new int[l_1][w_2]; // ???
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for(int i = 0; i < l_1; i++){
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int tmp = 0;
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for (int j = 0; j < w_2; j++){
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System.out.println(">>> i = " + i + ", j = " + j + ", tmp = " + tmp);
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tmp += (mat1[i][j] * mat2[j][i]);
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res[i][j] = tmp;
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}
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//res[i][j] = tmp; // ?
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}
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return res;
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}
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}

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