带权并查集 - How Many Answers Are Wrong

思路: 带权并查集+向量偏移

 #include <iostream>
 using namespace std;
 int n, m;
 int pre[];
 int f[];   // 到根节点的距离
 int ans = ;

 void init()
 {
     for (int i = ; i <= n; i++) {
         pre[i] = i;
         f[i] = ;
     }
 }

 int Find(int x)
 {
     if (x == pre[x])
         return x;
     int y = pre[x];
     pre[x] = Find(pre[x]);
     f[x] += f[y];
     return pre[x];
 }

 void Union(int x, int y, int s)
 {
     int fx = Find(x);
     int fy = Find(y);
     if (fx != fy) {
         pre[fx] = fy;
         f[fx] = f[y] + s - f[x];
     }
     else if (f[x] - s != f[y])
             ans++;
 }

 int main()
 {
     ios::sync_with_stdio(false);
     cin.tie();
     while (cin >> n >> m) {
         ans = ;
         init();
         for (int i = ; i < m; i++) {
             int a, b, s;
             cin >> a >> b >> s;
             Union(a - , b, s);
         }
         cout << ans << endl;
     }
     return ;
 }