普里姆算法

#include <stdio.h>
#define MAX 100
#define INF 0x3f3f3f3f
int graph[MAX][MAX];

int Prim(int graph[][MAX], int n)
{
    int lowcost[MAX], mst[MAX];
    int i, j, min, minid, sum = 0;

    for (i = 2; i <= n; i++)
    {
        lowcost[i] = graph[1][i];
        mst[i] = 1;
    }
    mst[1] = 0;
    for (i = 2; i <= n; i++)
    {
        min = INF;
        minid = 0;
        for (j = 2; j <= n; j++)
            if (lowcost[j] < min && lowcost[j] != 0)
            {
                min = lowcost[j];
                minid = j;
            }
        printf("(%d->%d) : %d\n", mst[minid], minid, min);
        sum += min;
        lowcost[minid] = 0;
        for (j = 2; j <= n; j++)
            if (graph[minid][j] < lowcost[j])
            {
                lowcost[j] = graph[minid][j];
                mst[j] = minid;
            }
    }
    return sum;
}

int main()
{
    freopen("input.txt", "r", stdin);
    int m, n, weight;

    scanf("%d %d", &m, &n);

    for (int i = 1; i <= m; i++)
        for (int j = 1; j <= m; j++)
            graph[i][j] = INF;
    for (int k = 0; k < n; k++)
    {
        int i, j;
        scanf("%d %d %d", &i, &j, &weight);

        graph[i][j] = weight;
        graph[j][i] = weight;
    }
    printf("最短路径=%d\n", Prim(graph, m));

    return 0;
}

input.txt

6 10
1 2 6
1 4 5
1 3 1
2 5 3
3 5 6
3 6 4
4 6 2
3 4 5
5 6 6
2 3 5