蓝桥杯2022省赛J题 - 推导部分和 -带权并查集datastructure

 

 

#include <bits/stdc++.h>
#define dbg(x) std::cerr << #x << "=" << x << "\n"
using i64 = long long;
const int N = 1e5 + 9;
i64 val[N];
int fa[N];
int find(int x){
    if(fa[x] == x) return x;
    int oldfa = fa[x];
    fa[x] = find(fa[x]);
    val[x] += val[oldfa];
    return fa[x];
}

int main(){
    std::ios::sync_with_stdio(false);
    std::cin.tie(nullptr);
    int n, m, q;
    std::cin >> n >> m >> q;
    for(int i = 1; i <= n ; i++){
        fa[i] = i;
    }
    for(int i = 1; i <= m ; i++){
        i64 L,R,S;
        std::cin >> L >> R >> S;
        L--;
        int fx = find(L), fy = find(R);
        fa[fy] = fx;
        val[fy] = val[L] - val[R] - S;
    }
    while(q--){
        i64 L, R;
        std::cin >> L >> R;
        L--;
        int fx = find(L), fy = find(R);
        if(fx != fy)
            std::cout<< "UNKNOWN" << "\n";
        else 
            std::cout<< val[L] - val[R] << "\n";
    }
    return 0;
}