xinyu04

摘要： There are $n$ cities. Some of them are connected, while some are not. If city $a$ is connected directly with city $b$, and city $b$ is connected direc 阅读全文

摘要： Given an m x n 2D binary grid grid which represents a map of '1's (land) and '0's (water), return the number of islands. An island is surrounded by wa 阅读全文

摘要： You are a cook in a remote area with no clocks or other way of keeping time other than a 4 minute hourglass and a 7 minute hourglass. You do have a st 阅读全文

摘要： Given four integer arrays nums1, nums2, nums3, and nums4 all of length n, return the number of tuples (i, j, k, l) such that: $0 \le i, j, k, l < n$ n 阅读全文