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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 a binary tree, find the lowest common ancestor (LCA) of two given nodes in the tree. According to the definition of LCA on Wikipedia: “The lowes 阅读全文
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The thief has found himself a new place for his thievery again. There is only one entrance to this area, called the "root." Besides the root, each hou 阅读全文
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Serialization is the process of converting a data structure or object into a sequence of bits so that it can be stored in a file or memory buffer, or 阅读全文
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Given the root of a tree, you are asked to find the most frequent subtree sum. The subtree sum of a node is defined as the sum of all the node values 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: Example 2: 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, return all duplicate subtrees. For each kind of duplicate subtrees, you only need to return the root node of any oneof them. Two 阅读全文
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Given a binary tree, find the length of the longest path where each node in the path has the same value. This path may or may not pass through the roo 阅读全文
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Given a binary tree, check whether it is a mirror of itself (ie, symmetric around its center). For example, this binary tree [1,2,2,3,4,4,3] is symmet 阅读全文
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Given a binary search tree and the lowest and highest boundaries as L and R, trim the tree so that all its elements lies in [L, R] (R >= L). You might 阅读全文
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Given a Binary Search Tree and a target number, return true if there exist two elements in the BST such that their sum is equal to the given target. E 阅读全文
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Given a non-empty binary tree, return the average value of the nodes on each level in the form of an array. Example 1: 阅读全文
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Given a binary tree, return the tilt of the whole tree. The tilt of a tree node is defined as the absolute difference between the sum of all left subt 阅读全文
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Given two non-empty binary trees s and t, check whether tree t has exactly the same structure and node values with a subtree of s. A subtree of s is a 阅读全文
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nvert a binary tree. to 方法二：BfS 阅读全文
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Given a non-empty special binary tree consisting of nodes with the non-negative value, where each node in this tree has exactly two or zero sub-node. 阅读全文
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Given two binary trees and imagine that when you put one of them to cover the other, some nodes of the two trees are overlapped while the others are n 阅读全文