用快读scanf别用cin

解题思路:
/*

带权并查集模板

*/
注意事项:

参考代码:

#include<bits/stdc++.h>

typedef long long ll;

using namespace std;

int fa[100005];

ll d[100005];

void initset(int n){

for(int i=0;i<=n;i++){

fa[i] = i;

d[i] = 0;

}

}

int find(int x){

if(x != fa[x]){

int t = fa[x];

fa[x] = find(fa[x]);

d[x] += d[t];

}

return fa[x];

}

void unionset(int x,int y,ll v){

int a = find(x);

int b = find(y);

fa[a] = b;

d[a] = d[y]+v-d[x];

}

int main(){

int n,m,q;

scanf("%d%d%d",&n,&m,&q);

initset(n);

for(int i=0;i<m;i++){

int a,b;

ll c;

scanf("%d%d%lld",&a,&b,&c);

a--;

unionset(a,b,c);

}

for(int i=0;i<q;i++){

int a,b;

scanf("%d%d",&a,&b); 

a--;

int na = find(a);

int nb = find(b);

if(na == nb){

ll ans = d[a]-d[b];

cout<<ans;

}

else{

cout<<"UNKNOWN";

}

cout<<"\n";

}

}