图论--最小生成树--Prim算法（带边输出）模板

#include <bits/stdc++.h>
using namespace std;
const int INF = 0x3f3f3f3f;
const int maxn = 1005;
bool vis[maxn];
int cost[maxn][maxn], lowc[maxn];
vector<int> demo;
int prim(int cost[][maxn], int n)
{
    int ans = 0;
    memset(vis, false, sizeof(vis));
    vis[0] = true;
    for(int i = 1; i < n; ++i)
        lowc[i] = cost[0][i];
    for(int i = 1; i < n; ++i)
    {
        int minc = INF;
        int p = -1;
        for(int j = 0; j < n; ++j)
        {
            if(!vis[j] && minc > lowc[j])
            {
                minc = lowc[j];
                p = j;
            }
        }
        if(minc == INF)
            return -1;
        ans += minc;
        demo.push_back(minc);
        vis[p] = true;
        for(int j = 0; j < n; ++j)
        {
            if(!vis[j] && lowc[j] > cost[p][j])
                lowc[j] = cost[p][j];
        }
    }
    return ans;
}

int main()
{
    int n, m, u, v, w;   //n是顶点数，m是边数
    scanf("%d %d", &m, &n);
    memset(cost, INF, sizeof(cost));
    //memset(vis, 0 ,sizeof(vis));
    for(int i = 0; i < m; ++i)
    {
        for(int j=0;j<m;j++)
        {
            cin>>cost[i][j];
            cost[j][i]=cost[i][j];
        }
    }
    //也可以通过边的数量输入数据 x y之间有 z长度的边，则连cost[x][y]=z
    prim(cost, m);
    for(int i=0;i<m-1;i++) cout<<demo[i]<<" ";
    return 0;
}