HDU 1213 How many table(dfs)

#include<iostream>using namespace std;const int maxn=1000+5;bool map[maxn][maxn],used[maxn];int n,m;void dfs(int u){    for(int v=1;v<=n;v++){        if(map[u][v]&&!used[v]){            used[v]=true;            dfs(v);        }    }}int main(){    int t;    scanf("%d",&t);    while(t--)    {        memset(map,false,sizeof(map));        scanf("%d%d",&n,&m);        for(int i=1;i<=m;i++){            int u,v;            scanf("%d%d",&u,&v);            map[u][v]=map[v][u]=true;        }        int ans=0;        memset(used,false,sizeof(used));        for(int i=1;i<=n;i++){            if(!used[i]) {ans++;dfs(i);}        }        printf("%d\n",ans);    }    return 0;}