[zoj解题] 1203

#include <stdio.h>
#include <stdlib.h>
#include <math.h>

#define MAXN 100
#define MAXM 9900

int N, M;

struct Edge {
    int u,v;
    double weight;
} edge[MAXM];

int vertexs[MAXN];
int parents[MAXN];
double xs[MAXN];
double ys[MAXN];

int edge_cmp(const void* a, const void* b) {
    return (((struct Edge*)a)->weight - ((struct Edge*)b)->weight > 0) ? 1:-1;
}

int parents_find(int x) {
    int s;
    for(s = x; parents[s] >= 0; s = parents[s]){
        ;
    }
    return s;
}

void parents_union(int r1, int r2) {
    int s1, s2;
    int tmp;
    s1 = parents_find(r1);
    s2 = parents_find(r2);
    tmp = parents[s1] + parents[s2];
    if(parents[s1] < parents[s2]) {
        parents[s2] = s1;
        parents[s1] = tmp;
    }
    else {
        parents[s1] = s2;
        parents[s2] = tmp;
    }
}

void kruskal(int count) {
    double sum_weight = 0;
    int num = 0;
    int i, u, v;
    for(i = 0; i < M; i++) {
        u = edge[i].u;
        v = edge[i].v;
        if(parents_find(u) != parents_find(v)) {
            num ++;
            sum_weight += edge[i].weight;
            parents_union(parents_find(u), parents_find(v));
        }
        if(num == N - 1) {
            break;
        }
    }
    printf("Case #%d:\n", count);
    printf("The minimal distance is: %.2lf\n", sum_weight);
}

int main() {
    int i, j;
    int index;
    double weight;
    int count = 1;
    int flag = 1;

    while(1) {
        scanf("%d", &N);
        if(N == 0) {
            break;
        }
        if(flag == 0) {
            printf("\n");
        }
        flag = 0;
        /* init */
        for(i = 0; i < N; i++) {
            vertexs[i] = i;
            parents[i] = -1;
        }

        for(i = 0; i < N; i++) {
            scanf("%lf%lf", &xs[i], &ys[i]);
        }

        index = 0;
        for(i = 0; i < N; i++) {
            for(j = i + 1; j < N; j++) {
                weight = sqrt((xs[i] - xs[j])*(xs[i] - xs[j]) + \
                              (ys[i] - ys[j])*(ys[i] - ys[j]));
                edge[index].u = i;
                edge[index].v = j;
                edge[index].weight = weight;
                index ++;
            }
        }
        M = index;
        /* sort */
        qsort(edge, M, sizeof(edge[0]), edge_cmp);
        kruskal(count);
        count ++;
    } 

    return 0;
}

　

有kruskal改的，格式很重要