competitive-programming/solved-lightOj/1174.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        111

vector<int> arr;
vector<int> e[NN];
int viw1[NN], viw2[NN];
queue<int> q;

int bfs1(int src) {
    mem(viw1, -1);
    viw1[src] = 0;
    q = queue<int>();
    q.push(src);
    int i, k, l;
    while (q.size()) {
        int u = q.front();
        q.pop();
        for (i = 0; i < e[u].size(); i++) {
            if (viw1[e[u][i]] == -1) {
                viw1[e[u][i]] = viw1[u] + 1;
                q.push(e[u][i]);
            }
        }
    }
}

int bfs2(int src) {
    mem(viw2, -1);
    viw2[src] = 0;
    q = queue<int>();
    q.push(src);
    int i, k, l;
    int ans = 0;
    while (q.size()) {
        int u = q.front();
        q.pop();
        ans = max(ans, viw1[u] + viw2[u]);
        for (i = 0; i < e[u].size(); i++) {
            if (viw2[e[u][i]] == -1) {
                viw2[e[u][i]] = viw2[u] + 1;
                q.push(e[u][i]);
            }
        }
    }
    return ans;
}

int main() {
    ios_base::sync_with_stdio(false);
    int t = 1, tc;
    cin >> tc;
    int i, j, k, l, m, n;
    while (tc--) {
        cin >> n >> m;

        for (i = 0; i <= n; i++) e[i].clear();
        for (i = 0; i < m; i++) {
            cin >> k >> l;
            e[k].pb(l);
            e[l].pb(k);
        }
        int src, dest;
        cin >> src >> dest;
        bfs1(src);
        int ans = bfs2(dest);
        printf("Case %d: %d\n", t++, ans);
    }
    return 0;
}