HDU-1102 Constructing Roads ( 最小生成树 )

#include<iostream>
#include<cstring>
using namespace std;

const int INF = 0x3f3f3f3f;
int n, q, ans;
int map[105][105];
int father[105];
bool flag[105];
int dis[105];

int findfather( int x ){
    while( x != father[x] )
        x = father[x];
    return x;
}

void prim(){
    ans = 0;
    memset( flag, false, sizeof( flag ) );

    for( int i = 1; i <= n; i++ )
        dis[i] = map[1][i];

    flag[1] = true;

    for( int t = 1; t < n; t++ ){
        int min = INF, mini;

        for( int i = 1; i <= n; i++){
            if( flag[i] ) continue;
            if( findfather( i ) == findfather( 1 ) ){ //使用并查集来进行区分合并
                mini = i;
                min = 0;
                break;
            }

            if( dis[i] < min ){
                min = dis[i];
                mini = i;
            }
        }

        flag[mini] = true;
        ans += min;
        father[findfather( mini )] = findfather( 1 );

        for( int j = 1; j <= n; j++ )
            if( dis[j] > map[mini][j] ){
                dis[j] = map[mini][j];
            }
    }
}

int main(){
    cin >> n;

    for( int i = 1; i <= n; i++ ){
        father[i] = i;

        for(int j = 1; j <= n; j++ )
            cin >> map[i][j];
    }

    cin >> q;
    int a,b;

    for( int i = 0; i < q; i++ ){
        cin >> a >> b;
        father[findfather( a )] = father[findfather( b )];
    }

    prim();

    cout << ans << endl;

    return 0;
}