백준 5567번 결혼식 C++

https://www.acmicpc.net/problem/5567

5567번: 결혼식

 

그래프 탐색 문제

 

#include <iostream>
#include <string>
#include <vector>
#include <math.h>
#include <algorithm>
#include <utility>
#include <stack>
#include <queue>
#include <math.h>
#include <set>
#include <map>
#include <list>
#include <unordered_map>
#include <unordered_set>
#include <iomanip>
#include <limits.h>

using namespace std;
using int64 = long long;

int n, m;
vector<vector<int>> graph;
vector<int> dists;

void dfs(int curr, int cnt) {
    if (dists[curr] == -1) {
        dists[curr] = cnt;
    }
    else {
        if (dists[curr] <= cnt) return;
        dists[curr] = cnt;
    }
    for (int i = 1; i <= n; i++) {
        if (graph[curr][i] == -1) continue;
        dfs(i, cnt + 1);
    }
}

int main() {
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);
    cout.tie(NULL);

    cin >> n >> m;
    graph = vector<vector<int>>(n + 1, vector<int>(n + 1, -1));
    dists = vector<int>(n + 1, -1);
    for (int i = 0; i < m; i++) {
        int a, b;
        cin >> a >> b;
        graph[a][b] = 1;
        graph[b][a] = 1;
    }
    dfs(1, 0);
    int ans = 0;
    for (int i = 2; i <= n; i++) {
        if (dists[i] == -1) continue;
        if (dists[i] <= 2) ans++;
    }
    cout << ans;
}