数据结构1 - 08-图7 公路村村通

 

 

 #include<stdio.h>
#include<string.h>
#define MAXN 1001
#define INF 0x3fffffff
int n,m,g[MAXN][MAXN],vis[MAXN],dist[MAXN];
void read();
int  prim();
int main(){
    read();
    int cost = prim();
    printf("%d\n",cost);
    return 0;
}
void read(){
    scanf("%d %d",&n,&m);
    int i,j,v1,v2,cost1;
    for(i=1;i<=n;i++)
        for(j=1;j<=n;j++)
            g[i][j] = INF;
    for(i=1;i<=m;i++){
        scanf("%d %d %d",&v1,&v2,&cost1);
        g[v1][v2] = cost1;
        g[v2][v1] = cost1;
    }
}
int prim(){
    int cost,i,j;
    for(i=1;i<=n;i++){
        dist[i] = INF;
        vis[i] = 0;
    }
    dist[1] = 0;
    vis[1] = 1;
    for(i=1;i<=n;i++)
        if(g[1][i]!=INF&&i!=1)
            dist[i] = g[1][i];
    cost = 0;
    while(1){
        int mdist=INF,mindex=-1;
        for(i=1;i<=n;i++){
            if(mdist>dist[i] && vis[i]==0){
                mdist = dist[i];
                mindex = i;
            }
        }
        if(mindex==-1) break;
        cost += mdist;
        vis[mindex] = 1;
        for(i=1;i<=n;i++){
            if(g[mindex][i]!=INF && i!=mindex && vis[i]==0){
                if(dist[i]>g[mindex][i]) dist[i] = g[mindex][i];
            }
        }
    }
    int vsum=0;
    for(i=1;i<=n;i++) vsum += vis[i];
    if (vsum==n) return cost;
    else return -1;
        
    
}