uva11631 - Dark roads

#include <cstdio>
#include <cstring>
#include <cstdlib>

using namespace std;

const int N = 200010;

int id
, u
, v
, w
;
int m, n;
int p
;

int cmp(const void *a, const void *b);
int find(int x);
int Union(int e);

int main()
{
int sum;
int cost;

#ifndef ONLINE_JUDGE
freopen("uva_in.txt", "r", stdin);
#endif

while (scanf("%d%d", &m, &n) == 2) {
if (m == 0 && n == 0) break;

sum = 0;
for (int i = 0; i < n; i++) {
id[i] = i;
scanf("%d%d%d", &u[i], &v[i], &w[i]);
sum += w[i];
}

memset(p, -1, sizeof(p));

qsort(id, n, sizeof(int), cmp);
cost = 0;
for (int i = 0; i < n; i++) {
cost += Union(id[i]);
}

printf("%d\n", sum - cost);
}
return 0;
}

int cmp(const void *a, const void *b)
{
int *pa = (int*)a;
int *pb = (int*)b;

return w[*pa] - w[*pb];
}

int find(int x)
{
return p[x] < 0 ? x : (p[x] = find(p[x]));
}

int Union(int e)
{
int a = u[e];
int b = v[e];

int pa = find(a), pb = find(b);

if (pa != pb) {
p[pb] = pa;
return w[e];
}

return 0;
}