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‎README.md‎

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111| [Minimum Depth of Binary Tree](https://leetcode.com/problems/minimum-depth-of-binary-tree/)|[Python](./leetcode_python/Recursion/minimum-depth-of-binary-tree.py), [Java](./leetcode_java/src/main/java/LeetCodeJava/Recursion/MinimumDepthOfBinaryTree.java)| _O(n)_ | _O(h)_ | Easy |`good basic`,`dfs`,`BST`,`amazon`,`fb`, LC 104| AGAIN******** (5)
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114| [Flatten Binary Tree to Linked List](https://leetcode.com/problems/flatten-binary-tree-to-linked-list/)| [Python](./leetcode_python/Recursion/flatten-binary-tree-to-linked-list.py)| _O(n)_ | _O(h)_ | Medium |`BST`, `dfs`, `M$`, `fb`| AGAIN**** (4)
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116| [Populating Next Right Pointers in Each Node](https://leetcode.com/problems/populating-next-right-pointers-in-each-node/)| [Python](./leetcode_python/Recursion/populating-next-right-pointers-in-each-node.py) | _O(n)_ | _O(1)_ | Medium |bfs, dfs, tree, recursion ,AGAIN,`fb`, amazon| AGAIN****** (5)
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117| [Populating Next Right Pointers in Each Node II](https://leetcode.com/problems/populating-next-right-pointers-in-each-node-ii/) |[Python](./leetcode_python/Recursion/populating-next-right-pointers-in-each-node-ii.py) | _O(n)_ | _O(h)_ | Medium | `Populating Next Right Pointers in Each Node I`, bfs, linked list, `amazon`, `fb`| AGAIN****** (3)
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117| [Populating Next Right Pointers in Each Node II](https://leetcode.com/problems/populating-next-right-pointers-in-each-node-ii/) |[Python](./leetcode_python/Recursion/populating-next-right-pointers-in-each-node-ii.py), [Java](./leetcode_java/src/main/java/LeetCodeJava/Recursion/PopulatingNextRightPointersInEachNode2.java)| _O(n)_ | _O(h)_ | Medium | `Populating Next Right Pointers in Each Node I`, bfs, linked list, `amazon`, `fb`, google| AGAIN****** (3)
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129| [Sum Root to Leaf Numbers](https://leetcode.com/problems/sum-root-to-leaf-numbers/) |[Python](./leetcode_python/Recursion/sum-root-to-leaf-numbers.py) | _O(n)_ | _O(h)_ | Medium |`trick`,`BST`, `dfs`, `fb`| AGAIN*** (4)
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156| [Binary Tree Upside Down](https://leetcode.com/problems/binary-tree-upside-down/) | [Python](./leetcode_python/Recursion/binary-tree-upside-down.py) | _O(n)_ | _O(1)_ | Medium |🔒| AGAIN (not start)
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241| [Different Ways to Add Parentheses](https://leetcode.com/problems/different-ways-to-add-parentheses/) | [Python](./leetcode_python/Recursion/different-ways-to-add-parentheses.py) | _O(n * 4^n / n^(3/2))_ | _O(n * 4^n / n^(3/2))_ | Medium || AGAIN (not start)
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666| [Path Sum IV](https://leetcode.com/problems/path-sum-iv/)| [Python](./leetcode_python/Breadth-First-Search/path-sum-iv.py) | _O(n)_ | _O(w)_ | Medium |🔒 Topological Sort | AGAIN* (3) (not start)
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742|[Closest Leaf in a Binary Tree](https://leetcode.com/problems/closest-leaf-in-a-binary-tree/)| [Python](./leetcode_python/Breadth-First-Search/closest-leaf-in-a-binary-tree.py), [Java](./leetcode_java/src/main/java/LeetCodeJava/BFS/ClosestLeafInaBinaryTree.java) | _O(n)_ | _O(n)_ | Medium | AGAIN, Graph, bfs+dfs, search, `good trick`, `amazon`| AGAIN********** (6)
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743|[Network Delay Time](https://leetcode.com/problems/network-delay-time/)| [Python](./leetcode_python/Breadth-First-Search/network-delay-time.py), [Java](./leetcode_java/src/main/java/LeetCodeJava/BFS/NetworkDelayTime.java) | _O(n)_ | _O(n)_ | Medium |Dijlstra, `google`| AGAIN **** (2)
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752|[Open the Lock](https://leetcode.com/problems/open-the-lock/)| [Python](./leetcode_python/Breadth-First-Search/open-the-lock.py), [Java](./leetcode_java/src/main/java/LeetCodeJava/BFS/OpenTheLock.java)s | _O(k * n^k + d)_ | _O(k * n^k + d)_ | Medium |LC 863, google | AGAIN (not start)
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752|[Open the Lock](https://leetcode.com/problems/open-the-lock/)| [Python](./leetcode_python/Breadth-First-Search/open-the-lock.py), [Java](./leetcode_java/src/main/java/LeetCodeJava/BFS/OpenTheLock.java) | _O(k * n^k + d)_ | _O(k * n^k + d)_ | Medium |LC 863, google | AGAIN (not start)
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787|[Cheapest Flights Within K Stops](https://leetcode.com/problems/cheapest-flights-within-k-stops/)| [Python](./leetcode_python/Breadth-First-Search/cheapest-flights-within-k-stops.py) | _O(\|E\| * log\|V\|)_ | _O(\|E\|)_ | Medium | `Dijkstra's algorithm`, dfs, bfs, graph, priority queue,`amazon`, apple, google, airbnb | AGAIN****** (3) (not start)
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815|[Bus Routes](https://leetcode.com/problems/bus-routes/)| [Python](./leetcode_python/Breadth-First-Search/bus-routes.py), [Java](./leetcode_java/src/main/java/LeetCodeJava/BFS/BusRoutes.java) | _O(\|E\| * log\|V\|)_ | _O(\|E\|)_ | Hard | shortest route, graph, bfs,`amazon`, google| AGAIN**** (3)
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886|[Possible Bipartition](https://leetcode.com/problems/possible-bipartition/)| [Python](./leetcode_python/Breadth-First-Search/possible-bipartition.py) | _O(\|V\| + \|E\|)_ | _O(\|V\| + \|E\|)_| Medium |check `# 785 Is Graph Bipartite?`,`graph`, `AGAIN`,`union find` ,`fb` | AGAIN********** (6)

‎leetcode_java/src/main/java/LeetCodeJava/Recursion/PopulatingNextRightPointersInEachNode2.java‎

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package LeetCodeJava.Recursion;
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// https://leetcode.com/problems/populating-next-right-pointers-in-each-node-ii/description/
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import java.util.LinkedList;
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import java.util.Queue;
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/**
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*
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Code
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Testcase
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Test Result
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Test Result
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117. Populating Next Right Pointers in Each Node II
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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 binary tree
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struct Node {
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int val;
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Node *left;
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Node *right;
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Node *next;
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}
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Populate each next pointer to point to its next right node. If there is no next right node, the next pointer should be set to NULL.
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Initially, all next pointers are set to NULL.
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Example 1:
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Input: root = [1,2,3,4,5,null,7]
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Output: [1,#,2,3,#,4,5,7,#]
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Explanation: Given the above binary tree (Figure A), your function should populate each next pointer to point to its next right node, just like in Figure B. The serialized output is in level order as connected by the next pointers, with '#' signifying the end of each level.
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Example 2:
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Input: root = []
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Output: []
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Constraints:
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The number of nodes in the tree is in the range [0, 6000].
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-100 <= Node.val <= 100
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Follow-up:
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You may only use constant extra space.
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The recursive approach is fine. You may assume implicit stack space does not count as extra space for this problem.
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*
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*
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*/
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public class PopulatingNextRightPointersInEachNode2 {
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/*
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// Definition for a Node.
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class Node {
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public int val;
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public Node left;
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public Node right;
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public Node next;
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public Node() {}
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public Node(int _val) {
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val = _val;
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}
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public Node(int _val, Node _left, Node _right, Node _next) {
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val = _val;
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left = _left;
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right = _right;
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next = _next;
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}
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};
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*/
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// TODO: move to dataStructure package
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class Node {
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public int val;
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public Node left;
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public Node right;
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public Node next;
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public Node() {}
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public Node(int _val) {
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val = _val;
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}
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public Node(int _val, Node _left, Node _right, Node _next) {
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val = _val;
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left = _left;
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right = _right;
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next = _next;
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}
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};
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// V0
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// public Node connect(Node root) {
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//
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// }
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// V1
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// https://leetcode.com/problems/populating-next-right-pointers-in-each-node-ii/solutions/5449615/my-easy-accepted-java-solution-100-by-di-nz2w/
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public Node connect_1(Node root) {
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if (root == null)
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return null;
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Queue<Node> queue = new LinkedList<>();
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queue.offer(root);
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while (!queue.isEmpty()) {
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int levelSize = queue.size();
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Node prev = null;
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for (int i = 0; i < levelSize; i++) {
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Node currentNode = queue.poll();
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if (prev != null) {
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prev.next = currentNode;
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}
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prev = currentNode;
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if (currentNode.left != null) {
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queue.offer(currentNode.left);
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}
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if (currentNode.right != null) {
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queue.offer(currentNode.right);
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}
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}
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}
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return root;
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}
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// V2-1
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// IDEA: BFS
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// https://leetcode.com/problems/populating-next-right-pointers-in-each-node-ii/solutions/2033511/3-approaches-bfs-bfs-linkedlist-recursio-0q68/
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// V2-2
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// IDEA: BFS + LINKEDLIST
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// https://leetcode.com/problems/populating-next-right-pointers-in-each-node-ii/solutions/2033511/3-approaches-bfs-bfs-linkedlist-recursio-0q68/
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// V2-3
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// IDEA: RECURSION
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// https://leetcode.com/problems/populating-next-right-pointers-in-each-node-ii/solutions/2033511/3-approaches-bfs-bfs-linkedlist-recursio-0q68/
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}

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