hdu 1233

赤裸裸的最小生成树

/*
 * hdu1233/linux.c
 * Created on: 2011-8-2
 * Author    : ben
 */
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <math.h>

#define MAXN 105

int map[105][105];
int N, M;
/**
 * 普里姆求最小生成树，返回最小生成树的权值，返回-1表示图不连通
 */
int MST_Prim() {
    int lowcost[MAXN];
    int i, j, k, minc, ret  = 0;
    for (k = 1; k < N; k++) {
        lowcost[k] = map[0][k];
    }
    lowcost[0] = 0;
    for(i = 1; i < N; i++) {
        minc = 0x7fffffff;
        for(j = 0; j < N; j++) {
            if(lowcost[j] > 0 && lowcost[j] < minc) {
                minc = lowcost[j];
                k = j;
            }
        }
        if(minc == 0x7fffffff) {
            return -1;
        }
        ret += minc;
        lowcost[k] = 0;
        for(j = 0; j < N; j++) {
            if(lowcost[j] > map[k][j]) {
                lowcost[j] = map[k][j];
            }
        }
    }
    return ret;
}

void buildmap() {
    int i, j, k;
    for (k = 0; k < M; k++) {
        scanf("%d%d", &i, &j);
        scanf("%d", &map[i - 1][j - 1]);
        map[j - 1][i - 1] = map[i - 1][j - 1];
    }
}

void work() {
    while (scanf("%d", &N) == 1 && N > 0) {
        M = N * (N - 1) / 2;
        buildmap();
        printf("%d\n", MST_Prim());
    }
}

int main() {
#ifndef ONLINE_JUDGE
    freopen("data.in", "r", stdin);
#endif
    work();
    return 0;
}