【唯一最小生成树】POJ 1679

#define N 105
int n,m;
int dis
,g

;
bool vis
;
int mx

;//记录路径i-j最大的边值
int pre
;//记录最小生成树路径
bool intree

;//判断哪些边属于MST
int prime(int s){
int i,j;
for(i=1;i<=n;i++){
dis[i] = g[s][i];
vis[i] = 0;
pre[i] = 1;
}
dis[s] = 0;
vis[s] = 1;
int ans = 0;
for(i=1;i<n;i++){
int minm = MAX;
int tmp;
for(j=1;j<=n;j++){
if(!vis[j] && dis[j]<minm){
minm = dis[j];
tmp = j;
}
}
if(minm==MAX)return -1;//不连通
vis[tmp] = 1;
intree[pre[tmp]][tmp] = intree[tmp][pre[tmp]] = true;
ans += minm;
for(j=1;j<=n;j++){
if(vis[j])
mx[j][tmp] = max(mx[j][pre[tmp]], g[pre[tmp]][tmp]);
}
for(j=1;j<=n;j++){
if(!vis[j] && dis[j]>g[tmp][j]){
dis[j] = g[tmp][j];
pre[j] = tmp;
}
}
}
return ans;
}
void init(){
int i,j;
for(i=1;i<=n;i++){
for(j=i+1;j<=n;j++){
g[i][j] = g[j][i] = MAX;
mx[i][j] = mx[j][i] = 0;
intree[i][j] = intree[j][i] = 0;
}
}
}
int main(){
int t;
scanf("%d",&t);
while(t--){
scanf("%d%d",&n,&m);
init();
int i,j;
while(m--){
int a,b,c;
scanf("%d%d%d",&a,&b,&c);
g[a][b] = g[b][a] = c;
}
int ans = prime(1);
if(ans<0){
printf("0\n");
continue;
}
bool ok = 0;
for(i=1;i<=n;i++){
for(j=i+1;j<=n;j++){
if(intree[i][j] || g[i][j]==MAX)continue;//排除已经属于MST和i,j没有边的情况
int res = ans - mx[i][j] + g[i][j];//用不属于MST的边替代i，j路径最大的边，如果只一样证明不唯一
if(res==ans){
ok = 1;
break;
}
}
if(ok)break;
}
if(ok)puts("Not Unique!");
else printf("%d\n",ans);
}
return 0;
}