题解 | #牛客春招刷题训练营#【模板】单源最短路Ⅰ ‖ 无权图

#include <iostream>
#include <queue>
#include <unordered_map>
#include <vector>
using namespace std;

int main() {
    int n, m, s, u, v;
    cin >> n >> m >> s;
    vector<int> len(n + 1, -1);
    unordered_map<int, vector<int>> mp;
    for (int i = 0; i < m; ++i) {
        cin >> u >> v;
        mp[u].push_back(v);
    }
    queue<int> q;
    len[s] = 0;
    q.push(s);
    while (!q.empty()) {
        int x = q.front();
        q.pop();
        if (mp.find(x) != mp.end()) {
            for (int& v : mp[x]) {
                if (len[v] == -1) {
                    q.push(v);
                    len[v] = len[x] + 1;
                }
            }
        }
    }
    for (int i = 1; i <= n; ++i) {
        cout << len[i] << " ";
    }
}
// 64 位输出请用 printf("%lld")