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Given a binary search tree, write a function kthSmallest to find the kth smallest element in it. Note:You may assume k is always valid, 1 ≤ k ≤ BST's 阅读全文
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Given n, how many structurally unique BST's (binary search trees) that store values 1 ... n? Example: Input: 3 Output: 5 Explanation: Given n = 3, the 阅读全文
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You need to find the largest value in each row of a binary tree. Example: Input: 1 / \ 3 2 / \ \ 5 3 9 Output: [1, 3, 9] # Definition for a binary tre 阅读全文
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Given a binary tree, find the leftmost value in the last row of the tree. Example 1: Input: 2 / \ 1 3 Output: 1 Example 2: Input: 1 / \ 2 3 / / \ 4 5 阅读全文
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Find the sum of all left leaves in a given binary tree. Example: 3 / \ 9 20 / \ 15 7 There are two left leaves in the binary tree, with values 9 and 1 阅读全文
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Given a binary tree, return the preorder traversal of its nodes' values. Example: Input: [1,null,2,3] 1 \ 2 / 3 Output: [1,2,3] Follow up: Recursive s 阅读全文
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Given a binary tree containing digits from 0-9 only, each root-to-leaf path could represent a number. An example is the root-to-leaf path 1->2->3 whic 阅读全文
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Given a binary tree and a sum, find all root-to-leaf paths where each path's sum equals the given sum. Note: A leaf is a node with no children. Exampl 阅读全文
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Given a binary tree, flatten it to a linked list in-place. For example, given the following tree: 1 / \ 2 5 / \ \ 3 4 6 The flattened tree should look 阅读全文
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Given a binary tree and a sum, determine if the tree has a root-to-leaf path such that adding up all the values along the path equals the given sum. N 阅读全文