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‎README.md‎

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276| [Paint Fence](https://leetcode.com/problems/paint-fence/) | [Python](./leetcode_python/Dynamic_Programming/paint-fence.py) | _O(n)_| _O(1)_| Easy |🔒| AGAIN
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279| [Perfect Squares](https://leetcode.com/problems/perfect-squares/)| [Python](./leetcode_python/Dynamic_Programming/perfect-squares.py) | _O(n * sqrt(n))_ | _O(n)_ | Medium | dp, bfs, trick, Hash, `google` | AGAIN*
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303| [Range Sum Query - Immutable](https://leetcode.com/problems/range-sum-query-immutable/)| [Python](./leetcode_python/Dynamic_Programming/range-sum-query-immutable.py) | ctor: _O(n)_, lookup: _O(1)_ | _O(n)_ | Easy || OK
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304| [Range Sum Query 2D - Immutable](https://leetcode.com/problems/range-sum-query-2d-immutable/)| [Python](./leetcode_python/Dynamic_Programming/range-sum-query-2d-immutable.py) | ctor: _O(m * n)_, lookup: _O(1)_ | _O(m * n)_ | Medium |`dp`,`trick`,`fb`| AGAIN******* (5)
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304| [Range Sum Query 2D - Immutable](https://leetcode.com/problems/range-sum-query-2d-immutable/)| [Python](./leetcode_python/Dynamic_Programming/range-sum-query-2d-immutable.py), [Java](./leetcode_java/src/main/java/LeetCodeJava/DynamicProgramming/RangeSumQuery2DImmutable.java) | ctor: _O(m * n)_, lookup: _O(1)_ | _O(m * n)_ | Medium |`dp`,`trick`,`fb`| AGAIN******* (5)
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309| [Best Time to Buy and Sell Stock with Cooldown](https://leetcode.com/problems/best-time-to-buy-and-sell-stock-with-cooldown/) | [Python](./leetcode_python/Dynamic_Programming/best-time-to-buy-and-sell-stock-with-cooldown.py) | _O(n)_ | _O(1)_ | Medium || AGAIN (not start)
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322| [Coin Change](https://leetcode.com/problems/coin-change/) | [Python](./leetcode_python/Dynamic_Programming/coin-change.py), [Java](./leetcode_java/src/main/java/LeetCodeJava/DynamicProgramming/CoinChange.java)| _O(n * k)_ | _O(k)_ | Medium |Curated Top 75, bfs, dfs, dp, grab, google, fb, apple, `amazon`| AGAIN************* (6) (MUST)
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351| [Android Unlock Patterns](https://leetcode.com/problems/android-unlock-patterns/) | [Python](./leetcode_python/Dynamic_Programming/android-unlock-patterns.py) | _O(9^2 * 2^9)_ | _O(9 * 2^9)_ | Medium | 🔒 Backtracking, DP, `google` | AGAIN (not start)

‎data/progress.md‎

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# Progress
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# 2024-12-08
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- https://github.com/yennanliu/CS_basics/blob/master/doc/Leetcode_company_frequency-master/Google%206months-%20LeetCode.pdf
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# 2024-11-30
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- https://github.com/yennanliu/CS_basics/blob/master/doc/Leetcode_company_frequency-master/Google%206months-%20LeetCode.pdf
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‎data/progress.txt‎

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20241208: 304
12
20241202: 370(todo),1109(todo)
23
20241130: 34,767
34
20241126: 722,380

‎data/to_review.txt‎

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2025-02-01 -> ['304']
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2025-01-26 -> ['370(todo),1109(todo)']
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2025-01-24 -> ['34,767']
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2025-01-20 -> ['722,380']
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2025-01-19 -> ['33,81']
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2025-01-17 -> ['253']
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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)']
8-
2025-01-11 -> ['394']
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2025-01-11 -> ['304', '394']
911
2025-01-10 -> ['833,950']
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2025-01-05 -> ['370(todo),1109(todo)']
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2025-01-04 -> ['53,210,207']
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2025-01-03 -> ['34,767', '444']
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2025-01-02 -> ['1188,130,855(again)']
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2024-12-30 -> ['722,380']
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2024-12-29 -> ['33,81']
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2024-12-29 -> ['304', '33,81']
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2024-12-28 -> ['900']
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2024-12-27 -> ['253', '26,27', '802,1197,26']
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2024-12-26 -> ['776,31']
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2024-12-25 -> ['004(todo),34(todo),162(todo),275(todo)']
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2024-12-24 -> ['986(todo),1229(todo),1868(todo),80(todo),209(todo),283(todo),360(todo),713(todo),532(todo),611(todo)']
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2024-12-21 -> ['34,767', '394', '855,846']
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2024-12-23 -> ['370(todo),1109(todo)']
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2024-12-21 -> ['304', '34,767', '394', '855,846']
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2024-12-20 -> ['833,950', '932']
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2024-12-18 -> ['951,792']
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2024-12-17 -> ['722,380']
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2024-12-16 -> ['33,81']
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2024-12-16 -> ['304', '33,81']
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2024-12-15 -> ['370(todo),1109(todo)']
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2024-12-14 -> ['253', '53,210,207', '163,1048']
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2024-12-13 -> ['34,767', '776,31', '444', '298,729']
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2024-12-13 -> ['304', '34,767', '776,31', '444', '298,729']
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2024-12-12 -> ['004(todo),34(todo),162(todo),275(todo)', '1188,130,855(again)', '1146']
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2024-12-11 -> ['986(todo),1229(todo),1868(todo),80(todo),209(todo),283(todo),360(todo),713(todo),532(todo),611(todo)']
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2024-12-09 -> ['722,380']
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2024-12-11 -> ['304', '986(todo),1229(todo),1868(todo),80(todo),209(todo),283(todo),360(todo),713(todo),532(todo),611(todo)']
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2024-12-10 -> ['304', '370(todo),1109(todo)']
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2024-12-09 -> ['304', '722,380']
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2024-12-08 -> ['34,767', '33,81', '394', '737']
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2024-12-07 -> ['833,950', '900', '686,734,737']
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2024-12-07 -> ['370(todo),1109(todo)', '833,950', '900', '686,734,737']
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2024-12-06 -> ['253', '26,27', '802,1197,26', '353']
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2024-12-05 -> ['34,767', '776,31', '528,334']
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2024-12-04 -> ['722,380', '004(todo),34(todo),162(todo),275(todo)']
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2024-12-03 -> ['34,767', '33,81', '986(todo),1229(todo),1868(todo),80(todo),209(todo),283(todo),360(todo),713(todo),532(todo),611(todo)', '1145']
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2024-12-05 -> ['370(todo),1109(todo)', '34,767', '776,31', '528,334']
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2024-12-04 -> ['370(todo),1109(todo)', '722,380', '004(todo),34(todo),162(todo),275(todo)']
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2024-12-03 -> ['370(todo),1109(todo)', '34,767', '33,81', '986(todo),1229(todo),1868(todo),80(todo),209(todo),283(todo),360(todo),713(todo),532(todo),611(todo)', '1145']
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2024-12-02 -> ['34,767']
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2024-12-01 -> ['34,767', '722,380', '253', '53,210,207']
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2024-11-30 -> ['33,81', '776,31', '394', '444', '855,846', '1145,1219']

‎leetcode_java/src/main/java/LeetCodeJava/DynamicProgramming/RangeSumQuery2DImmutable.java‎

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package LeetCodeJava.DynamicProgramming;
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// https://leetcode.com/problems/range-sum-query-2d-immutable/description/
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/**
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* 304. Range Sum Query 2D - Immutable
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* Solved
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* Medium
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* Topics
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* Companies
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* Given a 2D matrix matrix, handle multiple queries of the following type:
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*
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* Calculate the sum of the elements of matrix inside the rectangle defined by its upper left corner (row1, col1) and lower right corner (row2, col2).
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* Implement the NumMatrix class:
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*
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* NumMatrix(int[][] matrix) Initializes the object with the integer matrix matrix.
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* int sumRegion(int row1, int col1, int row2, int col2) Returns the sum of the elements of matrix inside the rectangle defined by its upper left corner (row1, col1) and lower right corner (row2, col2).
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* You must design an algorithm where sumRegion works on O(1) time complexity.
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*
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*
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*
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* Example 1:
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*
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*
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* Input
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* ["NumMatrix", "sumRegion", "sumRegion", "sumRegion"]
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* [[[[3, 0, 1, 4, 2], [5, 6, 3, 2, 1], [1, 2, 0, 1, 5], [4, 1, 0, 1, 7], [1, 0, 3, 0, 5]]], [2, 1, 4, 3], [1, 1, 2, 2], [1, 2, 2, 4]]
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* Output
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* [null, 8, 11, 12]
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*
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* Explanation
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* NumMatrix numMatrix = new NumMatrix([[3, 0, 1, 4, 2], [5, 6, 3, 2, 1], [1, 2, 0, 1, 5], [4, 1, 0, 1, 7], [1, 0, 3, 0, 5]]);
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* numMatrix.sumRegion(2, 1, 4, 3); // return 8 (i.e sum of the red rectangle)
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* numMatrix.sumRegion(1, 1, 2, 2); // return 11 (i.e sum of the green rectangle)
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* numMatrix.sumRegion(1, 2, 2, 4); // return 12 (i.e sum of the blue rectangle)
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*
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*
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* Constraints:
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*
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* m == matrix.length
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* n == matrix[i].length
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* 1 <= m, n <= 200
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* -104 <= matrix[i][j] <= 104
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* 0 <= row1 <= row2 < m
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* 0 <= col1 <= col2 < n
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* At most 104 calls will be made to sumRegion.
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*
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*/
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public class RangeSumQuery2DImmutable {
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/**
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* Your NumMatrix object will be instantiated and called as such:
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* NumMatrix obj = new NumMatrix(matrix);
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* int param_1 = obj.sumRegion(row1,col1,row2,col2);
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*/
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// V0
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// class NumMatrix {
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//
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// public NumMatrix(int[][] matrix) {
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//
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// }
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//
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// public int sumRegion(int row1, int col1, int row2, int col2) {
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//
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// }
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// }
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// V1
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// IDEA : DP
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// https://zxi.mytechroad.com/blog/dynamic-programming/leetcode-304-range-sum-query-2d-immutable/
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// https://www.youtube.com/watch?v=MSNSqU3BnXk
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class NumMatrix_1 {
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private int[][] sums;
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public NumMatrix_1(int[][] matrix) {
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if (matrix == null || matrix.length == 0 || matrix[0].length == 0) {
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return;
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}
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int m = matrix.length;
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int n = matrix[0].length;
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// Initialize the sums array
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sums = new int[m + 1][n + 1];
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for (int i = 1; i <= m; i++) {
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for (int j = 1; j <= n; j++) {
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sums[i][j] = matrix[i - 1][j - 1]
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+ sums[i - 1][j]
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+ sums[i][j - 1]
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- sums[i - 1][j - 1];
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}
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}
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}
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public int sumRegion(int row1, int col1, int row2, int col2) {
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return sums[row2 + 1][col2 + 1]
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- sums[row2 + 1][col1]
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- sums[row1][col2 + 1]
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+ sums[row1][col1];
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}
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}
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// V2
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// IDEA : DP
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// https://leetcode.com/problems/range-sum-query-2d-immutable/solutions/2104317/dp-visualised-interview-tips/
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class NumMatrix_2 {
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private int[][] sums;
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public NumMatrix_2(int[][] matrix) {
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int n = matrix.length;
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int m = matrix[0].length;
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sums = new int[n+1][m+1];
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for (int i=1; i<=n; i++)
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for (int j=1; j<=m; j++)
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sums[i][j] = sums[i-1][j] + sums[i][j-1] + matrix[i-1][j-1] - sums[i-1][j-1];
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}
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public int sumRegion(int row1, int col1, int row2, int col2) {
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int RED_RECTANGLE = sums[row2+1][col2+1];
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int PURPLE_RECTANGLES = sums[row1][col2+1] + sums[row2+1][col1];
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int BLUE_RECTANGLE = sums[row1][col1];
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return RED_RECTANGLE - PURPLE_RECTANGLES + BLUE_RECTANGLE;
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}
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}
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// V3
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// IDEA : DP
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// https://leetcode.com/problems/range-sum-query-2d-immutable/solutions/1204168/js-python-java-c-easy-4-rectangles-dp-solution-w-explanation/
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class NumMatrix_3 {
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long[][] dp;
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public NumMatrix_3(int[][] M) {
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int ylen = M.length + 1, xlen = M[0].length + 1;
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dp = new long[ylen][xlen];
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for (int i = 1; i < ylen; i++)
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for (int j = 1; j < xlen; j++)
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dp[i][j] = M[i-1][j-1] + dp[i-1][j] + dp[i][j-1] - dp[i-1][j-1];
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}
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public int sumRegion(int R1, int C1, int R2, int C2) {
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return (int)(dp[R2+1][C2+1] - dp[R2+1][C1] - dp[R1][C2+1] + dp[R1][C1]);
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}
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}
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}

‎leetcode_java/src/main/java/dev/workspace5.java‎

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return res;
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}
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// LC 304
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/**
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* Your NumMatrix object will be instantiated and called as such:
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* NumMatrix obj = new NumMatrix(matrix);
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* int param_1 = obj.sumRegion(row1,col1,row2,col2);
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*/
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// V0
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// 3.05 - 3.05 pm
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class NumMatrix {
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public NumMatrix(int[][] matrix) {
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}
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public int sumRegion(int row1, int col1, int row2, int col2) {
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return 0;
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}
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}
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}
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