摘要：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

摘要：Given a digit string, return all possible letter combinations that the number could represent. A mapping of digit to letters (just like on the telepho 阅读全文

摘要：新年啦，大家新年快乐~~ 由于新年呢,所以最近很少做题，今天终于有时间可以打打代码了 134. Gas Station. There are N gas stations along a circular route, where the amount of gas at station i is  阅读全文

摘要：Given a 2D board and a word, find if the word exists in the grid. The word can be constructed from letters of sequentially adjacent cell, where "adjac 阅读全文