Description Invert a binary tree. Example 1 1 / \ / \ 2 3 => 3 2 / \ 4 4    解题:题目要求讲二叉树的左子树和右子树对调一下,用递归来做很简单: /** * Definition of TreeNode: * public class TreeNode { * public int val; * public TreeNode left, right; * public TreeNode(int val) { * this…

Description 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. Example Given a binary tree as follow: 1 / \ 2 3 / \ 4 5 The minimum depth is …

Description Given a collection of intervals, merge all overlapping intervals. Example Given intervals => merged intervals: [ [ (1, 3), (1, 6), (2, 6), => (8, 10), (8, 10), (15, 18) (15, 18) ] ] Challenge O(n log n) time and O(1) extra space. 题意:给定一个…

I did it in a recursive way. There is another iterative way to do it. I will come back at it later. /** * Definition of TreeNode: * public class TreeNode { * public int val; * public TreeNode left, right; * public TreeNode(int val) { * this.val = val…

Description Given a sorted (increasing order) array, Convert it to create a binary tree with minimal height. There may exist multiple valid solutions, return any of them. Example Given [1,2,3,4,5,6,7], return 4 / \ 2 6 / \ / \ 1 3 5 7 解题:题目要求根据一个有序的数…

Description For the given binary tree, return a deep copy of it. Example Given a binary tree: 1 / \ 2 3 / \ 4 5 return the new binary tree with same structure and same value: 1 / \ 2 3 / \ 4 5 解题:链表复制.递归解法比较简单,代码如下: /** * Definition of TreeNode: * pu…

Given a binary search tree (BST) with duplicates, find all the mode(s) (the most frequently occurred element) in the given BST. Assume a BST is defined as follows: The left subtree of a node contains only nodes with keys less than or equal to the nod…

Big binary tree Time Limit: 4000/2000 MS (Java/Others)    Memory Limit: 65536/65536 K (Java/Others)Total Submission(s): 597    Accepted Submission(s): 207 Problem Description You are given a complete binary tree with n nodes. The root node is numbere…

Design an algorithm to encode an N-ary tree into a binary tree and decode the binary tree to get the original N-ary tree. An N-ary tree is a rooted tree in which each node has no more than N children. Similarly, a binary tree is a rooted tree in whic…

Description Write a method to replace all spaces in a string with %20. The string is given in a characters array, you can assume it has enough space for replacement and you are given the true length of the string. You code should also return the new…