dynamic programming
Codeforces #1113C
1113C C. Sasha and a Bit of Relax 题意 给一个数组，然后求满足 的[l, r]子序列有多少个，其中表示异或计算。 思路 关键点在于如果满足条件的[l,r]存在，那么
Codeforces #719 C
719C C. Efim and Strange Grade time limit per test 1 second memory limit per test 256 megabytes input standard input output standard output
Codeforces #721 C
721C C. Journey time limit per test 3 seconds memory limit per test 256 megabytes input standard input output standard output Recently Irina arrived to one of the most famous cities of Berland — the Berlatov city. There are n showplaces in the city, numbered from1 to n, and some of them are connected by one-directional roads. The roads in Berlatov are designed in a way such that there are nocyclic routes between showplaces.
POJ1458
POJ1458 Common Subsequence Time Limit: 1000MS Memory Limit: 10000K Total Submissions: 44778 Accepted: 18346 Description A subsequence of a given sequence is the given sequence with some elements (possible none) left out. Given a sequence X = < x1, x2, …, xm > another sequence Z = < z1, z2, …, zk > is a subsequence of X if there exists a strictly increasing sequence < i1, i2, …, ik > of indices of X such that for all j = 1,2,…,k, xij = zj. For example, Z = < a, b, f, c > is a subsequence of X = < a, b, c, f, b, c > with index sequence < 1, 2, 4, 6 >. Given two sequences X and Y the problem is to find the length of the maximum-length common subsequence of X and Y.