POJ.1287 Networking (Prim)

POJ.1287 Networking (Prim)

题意分析

1. 可能有重边，注意选择最小的边。
2. 编号依旧从1开始。
3. 直接跑prim即可。

代码总览

#include <cstdio>
#include <cstring>
#define nmax 105
#define inf 1e8+7
using namespace std;
int mp[nmax][nmax];
bool isfind  = true;
int n,m;
int totaldis =0;
void prim()
{
    int lowcost[nmax];
    int path[nmax];
    for(int j = 1;j<=n;++j){
        lowcost[j] = mp[1][j];
        path[j] = 1;
    }
    path[1] = 0;
    int nowmin,nowminid;
    for(int i =2 ;i<=n;++i){
        nowmin = inf;
        nowminid = 0;
        for(int j = 2;j<=n;++j){
            if(nowmin > lowcost[j] && lowcost[j] != 0){
                nowmin = lowcost[j];
                nowminid = j;
            }
        }
        if(nowmin == inf){
            isfind = false;
            return;
        }
        totaldis += nowmin;
        lowcost[nowminid] = 0;
        for(int j = 2;j<=n;++j){
            if(mp[nowminid][j] < lowcost[j]){
                lowcost[j] = mp[nowminid][j];
                path[j] = nowminid;
            }
        }
    }
}
int main()
{
    //freopen("in.txt","r",stdin);
    while(scanf("%d",&n) != EOF && n){
        scanf("%d",&m);
        int sta,end,dis;
        totaldis = 0;
        isfind =  true;
        for(int i = 1; i<=n;++i)
            for(int j = 1;j<=n;++j)
                mp[i][j] = inf;
        for(int i = 1; i<=m ;++i){
            scanf("%d %d %d",&sta,&end,&dis);
            if(mp[sta][end] != inf){
                int temp = mp[sta][end];
                if(dis < temp)
                    mp[sta][end] = mp[end][sta] = dis;
            }else{
                mp[sta][end] = mp[end][sta] = dis;
            }
        }
        prim();
        if(isfind == false) totaldis = 0;
        printf("%d\n",totaldis);
    }
    return 0;
}