【BZOJ3632】外太空旅行【随机化】【最大团】

【题目链接】

目测是个最大团问题，那么直接随机化...

/* Pigonometry */#include <cstdio>#include <cstdlib>#include <algorithm>using namespace std;const int maxn = 55;int n, ans, g[maxn][maxn], ord[maxn], vis[maxn], clo;inline int calc() {clo++;int res = 0;for(int i = 1; i <= n; i++) if(vis[i] != clo) {res++;vis[i] = clo;for(int j = i + 1; j <= n; j++) if(!g[ord[i]][ord[j]])vis[j] = clo;}return res;}int main() {scanf("%d", &n);while(1) {int u, v;if(scanf("%d%d", &u, &v) != EOF) g[u][v] = g[v][u] = 1;else break;}for(int i = 1; i <= n; i++) ord[i] = i;for(int T = 1; T <= 100000; T++) {for(int i = 1; i <= n; i++) swap(ord[i], ord[rand() % i + 1]);ans = max(ans, calc());}printf("%d\n", ans);return 0;}