HDU 5952 Counting Cliques——剪枝

剪就完事了

#include <bits/stdc++.h>
using namespace std;
const int maxn = 110;
int T, n, m, s, ans;
vector<int> G[maxn];
int mp[maxn][maxn], temp[maxn];
void dfs(int u, int sz) {
    if (sz == s) {
        ans++; return;
    }
    for (int i = 0; i < G[u].size(); i++) {
        int v = G[u][i];
        bool ok = true;
        for (int j = 1; j <= sz; j++) {
            if (!mp[v][temp[j]]) {
                ok = false;
                break;
            }
        }
        if (ok) {
            temp[sz+1] = v;
            dfs(v, sz+1);
        }
    }
}
int main() {
    scanf("%d", &T);
    while (T--) {
        scanf("%d%d%d", &n, &m, &s);
        for (int i = 1; i <= n; i++) G[i].clear();
        memset(mp, 0, sizeof(mp));
        ans = 0;
        while (m--) {
            int u, v;
            scanf("%d%d", &u, &v);
            if (u > v) swap(u, v);
            G[u].push_back(v);
            mp[u][v] = mp[v][u] = 1;
        }
        for (int i = 1; i <= n; i++) {
            temp[1] = i;
            dfs(i, 1);
        }
        printf("%d\n", ans);
    }
    return 0;
}