hrbustOJ 最小生成树问题(kruskal)

/*
Name: 最小生成树(kruskal)
Copyright:
Author: Try86
Date: 15/04/12 08:01
Description:
*/

#include <cstdio>
#include <cstdlib>
#include <iostream>

using namespace std;

const int N = 10005;
const int M = 50005;

int p
, sum;
struct edge {
int u;
int v;
int w;
}e[M];

int cmp(const void *a, const void *b) {
return (*(edge *)a).w - (*(edge *)b).w;
}

void init(int vs) {
for (int i=1; i<=vs; ++i) p[i] = i;
return ;
}

int find(int v) {
if (p[v] != v) p[v] = find(p[v]);
return p[v];
}

int join(edge e) {
int x, y;
x = find(e.u);
y = find(e.v);
if (x != y) {
++sum;
p[x] = y;
return e.w;
}
return 0;
}

int kruskal(int es, int vs) {
int ans = 0;
init(vs);
qsort(e, es, sizeof(edge), cmp);
sum = 1;
for (int i=0; i<es; ++i) {
ans += join(e[i]);
if (sum == vs) return ans;
}
return -1;
}

int main() {
int n, m;
while (scanf("%d%d", &n, &m) != EOF) {
for (int i=0; i<m; ++i) scanf ("%d%d%d", &e[i].u, &e[i].v, &e[i].w);
int ans = kruskal(m, n);
printf ("%d\n", ans);
}
return 0;
}