摘要：
On a 2-dimensional grid, there are 4 types of squares: 1 represents the starting square. There is exactly one starting square. 2 represents the ending 阅读全文
摘要：
Given a binary tree with N nodes, each node has a different value from {1, ..., N}. A node in this binary tree can be flipped by swapping the left chi 阅读全文
摘要：
Given an array nums of integers, you can perform operations on the array. In each operation, you pick any nums[i] and delete it to earn nums[i] points 阅读全文