C++(씨쁠쁠)(cplusplus)-백준(baekjoon)(BaekJoon)코딩 2644번:촌수계산 답

#include <iostream>
#include <queue>
#include <vector>
using namespace std;
 
vector <int> family[101];
queue <int> q;
int n, m, a, b;
bool c[101];
int d[101];
 
int BFS(int x)
{
    q.push(x);
    c[x] = 1;
    while (!q.empty())
    {
        int x = q.front();
        q.pop();
        for (int i = 0; i < family[x].size(); i++)
        {
            int y = family[x][i];
            if (c[y] == 0)
            {
                q.push(y);
                c[y] = 1;
                d[y] = d[x] + 1;
                if (y == b)
                    return d[y];
            }
        }
    }
    return -1;
}
int main() {
 
    cin >> n;
    cin >> a >> b;
    cin >> m;
    while (m--)
    {
        int x, y;
        cin >> x >> y;
        family[x].push_back(y);
        family[y].push_back(x);
    }
    cout << BFS(a) << '\n';
}