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hcx2013
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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 leaf node.   /** * Definition for a binary tree node. * public class TreeNode { * int val; * TreeNode left; * TreeNode right; ...

Balanced Binary Tree

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 depth of the two subtrees of every node never differ by more than 1.   /** * Definition for a binary tree node. * public class TreeNode { * i ...
Given a singly linked list where elements are sorted in ascending order, convert it to a height balanced BST.   /** * Definition for singly-linked list. * public class ListNode { * int val; * ListNode next; * ListNode(int x) { val = x; } * } */ /** * Definition for a b ...
Given an array where elements are sorted in ascending order, convert it to a height balanced BST.   /** * Definition for a binary tree node. * public class TreeNode { * int val; * TreeNode left; * TreeNode right; * TreeNode(int x) { val = x; } * } */ public class S ...
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 example:Given binary tree {3,9,20,#,#,15,7}, 3 / \ 9 20 / \ 15 7   return its bottom-up level order traversal as: [ ...

LRU Cache

Design and implement a data structure for Least Recently Used (LRU) cache. It should support the following operations: get and set. get(key) - Get the value (will always be positive) of the key if the key exists in the cache, otherwise return -1.set(key, value) - Set or insert the value if the key ...
Given inorder and postorder traversal of a tree, construct the binary tree.   /** * Definition for a binary tree node. * public class TreeNode { * int val; * TreeNode left; * TreeNode right; * TreeNode(int x) { val = x; } * } */ public class Solution { public Tre ...
Given preorder and inorder traversal of a tree, construct the binary tree.   /** * Definition for a binary tree node. * public class TreeNode { * int val; * TreeNode left; * TreeNode right; * TreeNode(int x) { val = x; } * } */ public class Solution { public ...
Given a binary tree, find its maximum depth. The maximum depth is the number of nodes along the longest path from the root node down to the farthest leaf node.   /** * Definition for a binary tree node. * public class TreeNode { * int val; * TreeNode left; * TreeNode right; ...
Given a binary tree, return the zigzag level order traversal of its nodes' values. (ie, from left to right, then right to left for the next level and alternate between). For example:Given binary tree {3,9,20,#,#,15,7}, 3 / \ 9 20 / \ 15 7   return its zigzag level order ...
Given a binary tree, return the level order traversal of its nodes' values. (ie, from left to right, level by level). For example:Given binary tree {3,9,20,#,#,15,7}, 3 / \ 9 20 / \ 15 7   return its level order traversal as: [ [3], [9,20], [15,7] ] /* ...

Symmetric Tree

Given a binary tree, check whether it is a mirror of itself (ie, symmetric around its center). For example, this binary tree is symmetric: 1 / \ 2 2 / \ / \ 3 4 4 3   But the following is not: 1 / \ 2 2 \ \ 3 3 /** * Definition for a binary tre ...
Two elements of a binary search tree (BST) are swapped by mistake. Recover the tree without changing its structure. Note:A solution using O(n) space is pretty straight forward. Could you devise a constant space solution?   confused what "{1,#,2,3}" means? > read more on how binary t ...

Same Tree

Given two binary trees, write a function to check if they are equal or not. Two binary trees are considered equal if they are structurally identical and the nodes have the same value.   /** * Definition for a binary tree node. * public class TreeNode { * int val; * TreeNode left; ...

基本字符串压缩

题目描述 利用字符重复出现的次数,编写一个方法,实现基本的字符串压缩功能。比如,字符串“aabcccccaaa”经压缩会变成“a2b1c5a3”。若压缩后的字符串没有变短,则返回原先的字符串。 给定一个string iniString为待压缩的串(长度小于等于3000),保证串内字符均由大小写英文字母组成,返回一个string,为所求的压缩后或未变化的串。 测试样例 "aabcccccaaa" 返回:"a2b1c5a3"   "welcometonowcoderrrrr" 返回:"welcometonow ...
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