POJ1679 The Unique MST

#include <stdio.h>
#include <string.h>
#include <algorithm>
using namespace std;

typedef __int64 lld;
const int INF = ~0u>>1;
#define REP(i,a,b) for(int i=(a); i<(b); i++)
#define FOR(i,a,b) for(int i=(a); i<=(b); i++)
#define clr(a,b) memset(a,b,sizeof(a))

const int MAXN = 110;
int n,m;
struct edge {
int u,v,w;
int col;
int mark;
int ban;
bool operator < (const edge &tt) const {
return w < tt.w;
}
}g[MAXN*MAXN*MAXN];
int fa[MAXN];
int ok;
int first;

int Find(int x) {
return fa[x] = (fa[x] == x) ? x : Find(fa[x]);
}

int merge(int a, int b) {
a = Find(a);
b = Find(b);
if(a == b) return 0;
fa[a] = b;
return 1;
}

lld Kruskal() {
lld ret = 0;
FOR(i,0,n) fa[i] = i;
REP(i,0,m) {
if(g[i].ban) continue;
if(merge(g[i].u,g[i].v)) {

ret += (lld)g[i].w;
if(first && g[i].col) g[i].mark = 1, ok = 0;
}
}
return ret;
}

int main() {
int cas;
scanf("%d", &cas);
while(cas--) {
scanf("%d%d", &n ,&m);
REP(i,0,m) {
scanf("%d%d%d", &g[i].u,&g[i].v,&g[i].w);
g[i].col = 0;
g[i].mark = 0;
g[i].ban = 0;
}
sort(g,g+m);
REP(i,1,m) {
if(g[i].w == g[i-1].w) {
g[i].col = g[i-1].col = 1;
}
}
lld ans;
ok = 1;
first = 1;
ans = Kruskal();
if(ok) printf("%I64d\n", ans);
else {
int i;
first = 0;
for(i=0; i<m; i++) {
if(g[i].mark == 1) {
g[i].ban = 1;
lld tt = Kruskal();
if(tt == ans) break;
g[i].ban = 0;
}
}
if(i != m) printf("Not Unique!\n");
else printf("%I64d\n", ans);
}
}
return 0;
}