519
LeetCode 519. Random Flip Matrix 哈希Map
There is an `m x n` binary grid matrix with all the values set 0 initially. Design an algorithm to randomly pick an index `(i, j)` where `matrix[i][j] ......
CF519E A and B and Lecture Rooms
[题目链接](https://codeforces.com/problemset/problem/519/E) # 题目 见链接。 # 题解 **知识点:倍增,LCA,树型dp。** 要找到距离两点 $u,v$ 相同的点个数,我可以分类讨论: 1. $u,v$ 是同一个点,那么全部点都可以。 2. ......