BFS

#include <cstdio>
#include <vector>
#include <queue>
using namespace std;
int main()
{
    int n, i, j, vBegin, vEnd, x, current;
    scanf("%d", &n);
    vector < vector <int> > list(n);
    for(i = 0; i < n; i++)
    {
        for(j = 0; j < n; j++)
        {
            scanf("%d", &x);
            if(x)
            {
                list[i].push_back(j);
                list[j].push_back(i);
            }
        }
    }
    scanf("%d%d", &vBegin, &vEnd);
    vBegin--, vEnd--;
    queue <int> q;
    q.push(vBegin);
    vector <int> len(n, -1);
    len[vBegin] = 0;
    while(true)
    {
        if(q.empty())
        {
            printf("-1");
            return 0;
        }
        current = q.front();
        q.pop();
        if(current == vEnd)
        {
            printf("%d", len[vEnd]);
            return 0;
        }
        for(int next : list[current])
        {
            if(len[next] == -1)
            {
                q.push(next);
                len[next] = len[current] + 1;
            }
        }
    }
}