competitive-programming/solved-uva/11770.cpp at master · the-redback/competitive-programming · GitHub

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/**
 *                                   ____
 *       ____ ___  ____ ________  __/ __/
 *      / __ `__ \/ __ `/ ___/ / / / /_
 *     / / / / / / /_/ / /  / /_/ / __/
 *    /_/ /_/ /_/\__,_/_/   \__,_/_/
 *
 *    @link : https://the-redback.com
 */
#include <bits/stdc++.h>
using namespace std;

#define ppb       pop_back
#define pb(x)     push_back(x)
#define all(x)    x.begin(), x.end()
#define mem(a, b) memset(a, b, sizeof(a))
#define inf       1000000000
#define eps       1e-9
#define NN        10010

vector<int> e[NN];
int color[NN];
int fl;
vector<int> arr;

void dfs1(int u) {
    color[u] = 1;
    for (int i = 0; i < e[u].size(); i++) {
        int v = e[u][i];
        if (!color[v]) dfs1(v);
    }
    arr.pb(u);
    return;
}

void dfs2(int u) {
    color[u] = 1;
    for (int i = 0; i < e[u].size(); i++) {
        int v = e[u][i];
        if (!color[v]) dfs2(v);
    }
    return;
}

int main() {
    ios_base::sync_with_stdio(false);
    int t = 0, tc;
    int n, m, i, j, l, k;
    cin >> tc;
    while (tc--) {
        cin >> n >> m;
        int r = 0;
        for (i = 0; i < m; i++) {
            cin >> k >> l;
            e[k].pb(l);
        }
        mem(color, 0);
        fl = 0;
        for (i = 1; i <= n; i++) {
            if (!color[i]) dfs1(i);
        }
        mem(color, 0);
        int cnt = 0;
        reverse(all(arr));
        for (i = 0; i < arr.size(); i++) {
            if (!color[arr[i]]) {
                dfs2(arr[i]);
                cnt++;
            }
        }
        printf("Case %d: %d\n", ++t, cnt);
        for (i = 0; i <= n; i++) e[i].clear();
        arr.clear();
    }
    return 0;
}