City and flood.cpp

#include <cstdio>
#include <vector>
#include <queue>
using namespace std;
int main()
{
    int m, n, i, j, a, b, cont = 0, z;
    scanf("%d%d", &n, &m);
    vector<int> v [n+1];
    int imperio[n+1];
    queue<int> f;
    for(i=0;i<m;i++)
    {
        scanf("%d %d", &a, &b);
        v[a].push_back(b);
        v[b].push_back(a);
    }
   for(i=1;i<=n;i++)
    imperio[i] = -1;

    for(i=1;i<=n;i++)
    {
        if(imperio[i] == -1)
        {
            cont++;
            imperio[i] = cont;
            f.push(i);
            while(!f.empty())
            {
                z = f.front();
                f.pop();
                for(j=0;j<v[z].size();j++)
                {
                    if(imperio[v[z][j]] == -1){
                        imperio[v[z][j]] = imperio[z];
                        f.push(v[z][j]);
                    }
                }
            }
        }
    }
    printf("%d", cont);
}