prim(最小生成树）

#include <iostream>
#include <cstdio>
#include <cstring>
#define INF 0x7fffffff
#define maxn 100
using namespace std;
int n, m;
int edge[maxn][maxn];
int lowcost[maxn];
int nearvex[maxn];

void prim(int u0) {
    int i, j;
    int sumweight = 0;
    for( i = 1; i <= n; i++ ) {
        lowcost[i] = edge[u0][i];
        nearvex[i] = u0;
    }
    nearvex[u0] = -1;
    for( i = 1; i <= n; i++ ) {
        int minx = INF;
        int v = -1;
        for( j = 1; j <= n; j++ ) {
            if( nearvex[j] != -1 && lowcost[j] < minx ) {
                v = j;
                minx = lowcost[j];
            }
        }
        if( v != -1) {
            printf( "%d  %d  %d\n", nearvex[v], v, lowcost[v] );
            nearvex[v] = -1;
            sumweight += lowcost[v];
            for( j = 1; j <= n; j++ ) {
                if( nearvex[j] != -1 && edge[v][j] < lowcost[j] ) {
                    lowcost[j] = edge[v][j];
                    nearvex[j] = v;
                }
            }
        }
    }
    printf("weight of MST if %d\n", sumweight);
}

void input() {
    int i, j;
    memset(edge, 0, sizeof(edge));
    scanf("%d%d", &n, &m);
    int u, v, w;
    for( i = 1; i <= m; i++ ) {
        scanf("%d%d%d", &u, &v, &w);
        edge[u][v] = edge[v][u] = w;
    }
    for( i = 1; i <= n; i++ ) {
        for( j = 1; j <= n; j++ ) {
            if( i== j ) { edge[i][j] = 0 ; }
            else if(edge[i][j] == 0 ) {
                edge[i][j] = INF;
            }
        }
    }
}

int main()
{
    int start = 0;
    input();
    scanf("%d", &start);
    prim(start);
    return 0;
}
/************************
测试数据：
7 9
1 2 28
1 6 10
2 3 16
2 7 14
3 4 12
4 5 22
4 7 18
5 6 25
5 7 24
3
***************************/