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Given a binary tree, return all root-to-leaf paths. For example, given the following binary tree: 1 / \ 2 3 \ 5 All root-to-leaf paths are: ["1->2->5" 阅读全文
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Given a binary tree, return the bottom-up level order traversal of its nodes' values. (ie, from left to right, level by level from leaf to root). For 阅读全文
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Invert a binary tree. 4 / \ 2 7 / \ / \ 1 3 6 9 to 4 / \ 7 2 / \ / \ 9 6 3 1 Trivia:This problem was inspired by this original tweet by Max Howell: Go 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 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. F 阅读全文
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题目描述 用两个栈来实现一个队列，完成队列的Push和Pop操作。 队列中的元素为int类型。 1 import java.util.Stack; 2 3 public class Solution { 4 Stack<Integer> stack1 = new Stack<Integer>(); 阅读全文
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Given a binary tree, find its minimum depth. The minimum depth is the number of nodes along the shortest path from the root node down to the nearest l 阅读全文
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Given a binary tree, determine if it is height-balanced. For this problem, a height-balanced binary tree is defined as a binary tree in which the dept 阅读全文
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题目描述 输入某二叉树的前序遍历和中序遍历的结果，请重建出该二叉树。假设输入的前序遍历和中序遍历的结果中都不含重复的数字。例如输入前序遍历序列{1,2,4,7,3,5,6,8}和中序遍历序列{4,7,2,1,5,3,8,6}，则重建二叉树并返回。 思路： 前序遍历中，第一个点是根结点，根据这个根节点 阅读全文
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Given an array where elements are sorted in ascending order, convert it to a height balanced BST. 本质就是寻找分割点，分割点作为当前节点，然后递归左区间和右区间。 分割点就是数组中间位置的节点。 那么为 阅读全文