【HDOJ】3047 Zjnu Stadium

带权并查集。

 /* 3047 */
 #include <iostream>
 #include <string>
 #include <map>
 #include <queue>
 #include <set>
 #include <stack>
 #include <vector>
 #include <deque>
 #include <algorithm>
 #include <cstdio>
 #include <cmath>
 #include <ctime>
 #include <cstring>
 #include <climits>
 #include <cctype>
 #include <cassert>
 #include <functional>
 #include <iterator>
 #include <iomanip>
 using namespace std;
 //#pragma comment(linker,"/STACK:102400000,1024000")

 #define sti                set<int>
 #define stpii            set<pair<int, int> >
 #define mpii            map<int,int>
 #define vi                vector<int>
 #define pii                pair<int,int>
 #define vpii            vector<pair<int,int> >
 #define rep(i, a, n)     for (int i=a;i<n;++i)
 #define per(i, a, n)     for (int i=n-1;i>=a;--i)
 #define clr                clear
 #define pb                 push_back
 #define mp                 make_pair
 #define fir                first
 #define sec                second
 #define all(x)             (x).begin(),(x).end()
 #define SZ(x)             ((int)(x).size())
 #define lson            l, mid, rt<<1
 #define rson            mid+1, r, rt<<1|1

 const int maxn = 5e4+;
 int fa[maxn], dis[maxn];

 int find(int x) {
     if (fa[x] == x)
         return x;

     int tmp = fa[x];
     fa[x] = find(fa[x]);
     dis[x] += dis[tmp];

     return fa[x];
 }

 bool merge(int u, int v, int w) {
     int fu = find(u);
     int fv = find(v);

     if (fu == fv) {
         if (dis[u]+w!=dis[v])
             return false;
         return true;
     }

     fa[fv] = fu;
     dis[fv] = dis[u] + w - dis[v];

     return true;
 }

 int main() {
     ios::sync_with_stdio(false);
     #ifndef ONLINE_JUDGE
         freopen("data.in", "r", stdin);
         freopen("data.out", "w", stdout);
     #endif

     int n, m;
     int u, v, w;
     int ans;

     while (scanf("%d %d", &n, &m) != EOF) {
         rep(i, , n+) {
             fa[i] = i;
             dis[i] = ;
         }
         ans = ;
         while (m--) {
             scanf("%d %d %d", &u, &v, &w);
             if (!merge(u, v, w))
                 ++ans;
         }
         printf("%d\n", ans);
     }

     #ifndef ONLINE_JUDGE
         printf("time = %d.\n", (int)clock());
     #endif

     return ;
 }