James Pan

原题网址：https://leetcode.com/problems/wiggle-sort/ Given an unsorted array nums, reorder it in-place such that nums[0] = nums[2] . For example, given nums = [3, 5, 2, 1, 6, 4], one possible ans

原题网址：https://leetcode.com/problems/spiral-matrix-ii/ Given an integer n, generate a square matrix filled with elements from 1 to n2 in spiral order. For example, Given n = 3, You should retu

原题网址：https://leetcode.com/problems/validate-binary-search-tree/ Given a binary tree, determine if it is a valid binary search tree (BST). Assume a BST is defined as follows: The left subtre

原题网址：https://leetcode.com/problems/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:

原题网址：https://leetcode.com/problems/binary-tree-level-order-traversal/ Given a binary tree, return the level order traversal of its nodes' values. (ie, from left to right, level by level). For

原题网址：https://leetcode.com/problems/binary-tree-zigzag-level-order-traversal/ Given a binary tree, return the zigzag level order traversal of its nodes' values. (ie, from left to right, then right

原题网址：https://leetcode.com/problems/binary-tree-postorder-traversal/ Given a binary tree, return the postorder traversal of its nodes' values. For example: Given binary tree {1,#,2,3}, 1

原题网址：https://leetcode.com/problems/binary-tree-inorder-traversal/ Given a binary tree, return the inorder traversal of its nodes' values. For example: Given binary tree {1,#,2,3}, 1

原题网址：https://leetcode.com/problems/reconstruct-itinerary/ Given a list of airline tickets represented by pairs of departure and arrival airports [from, to], reconstruct the itinerary in order.

原题网址：https://leetcode.com/problems/recover-binary-search-tree/ Two elements of a binary search tree (BST) are swapped by mistake. Recover the tree without changing its structure. Note: A sol

原题网址：https://leetcode.com/problems/spiral-matrix/ Given a matrix of m x n elements (m rows, n columns), return all elements of the matrix in spiral order. For example, Given the following mat

原题网址：https://leetcode.com/problems/rotate-image/ You are given an n x n 2D matrix representing an image. Rotate the image by 90 degrees (clockwise). Follow up: Could you do this in-place?

原题网址：https://leetcode.com/problems/zigzag-conversion/ The string "PAYPALISHIRING" is written in a zigzag pattern on a given number of rows like this: (you may want to display this pattern in a

原题网址：https://leetcode.com/problems/zigzag-iterator/ Given two 1d vectors, implement an iterator to return their elements alternately. For example, given two 1d vectors: v1 = [1, 2] v2 = [3, 4

原题网址：https://leetcode.com/problems/construct-binary-tree-from-preorder-and-inorder-traversal/ Given preorder and inorder traversal of a tree, construct the binary tree. Note: You may assume t

原题网址：https://leetcode.com/problems/construct-binary-tree-from-inorder-and-postorder-traversal/ Given inorder and postorder traversal of a tree, construct the binary tree. Note: You may assume

原题网址：https://leetcode.com/problems/binary-tree-level-order-traversal-ii/ Given a binary tree, return the bottom-up level order traversal of its nodes' values. (ie, from left to right, level by le

原题网址：https://leetcode.com/problems/path-sum/ 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.

原题网址：https://leetcode.com/problems/flatten-binary-tree-to-linked-list/ Given a binary tree, flatten it to a linked list in-place. For example, Given 1 / \ 2 5

原题网址：https://leetcode.com/problems/binary-tree-longest-consecutive-sequence/ Given a binary tree, find the length of the longest consecutive sequence path. The path refers to any sequence

原题网址：https://leetcode.com/problems/binary-tree-vertical-order-traversal/ Given a binary tree, return the vertical order traversal of its nodes' values. (ie, from top to bottom, column by column).

原题网址：https://leetcode.com/problems/house-robber-iii/ 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,

原题网址：https://leetcode.com/problems/verify-preorder-serialization-of-a-binary-tree/ One way to serialize a binary tree is to use pre-order traversal. When we encounter a non-null node, we record t