hdu 3047 Zjnu Stadium（并查集）

 1 #include<iostream>
 2 #include<cstdio>
 3 #include<cstdlib>
 4 #include<cstring>
 5 #include<string>
 6 #include<queue>
 7 #include<algorithm>
 8 #include<map>
 9 #include<iomanip>
10 #include<climits>
11 #include<string.h>
12 #include<cmath>
13 #include<stdlib.h>
14 #include<vector>
15 #include<stack>
16 #include<set>
17 #define INF 1e7
18 #define MAXN 10010
19 #define maxn 1000010
20 #define Mod 1000007
21 #define N 1010
22 using namespace std;
23 typedef long long LL;
24 
25 int n, m;
26 int fa[50010];
27 int dis[50010];
28 
29 int findset(int x)
30 {
31     if (x == fa[x]) return x;
32     int t = fa[x];
33     fa[x] = findset(fa[x]);
34     dis[x] += dis[t];
35     return fa[x];
36 }
37 
38 bool merg(int a, int b, int w)
39 {
40     int x = findset(a);
41     int y = findset(b);
42     if (x == y) {
43         if (dis[a] + w != dis[b]) return false;
44         return true;
45     }
46     fa[y] = x;
47     dis[y] = dis[a] + w - dis[b];
48     return true;
49 }
50 
51 int main()
52 {
53     int a, b, w;
54     while (~scanf("%d%d",&n,&m)) {
55         for (int i = 0; i <= n; ++i)
56             fa[i] = i, dis[i] = 0;
57         int ans = 0;
58         for (int i = 0; i < m; ++i) {
59             scanf("%d%d%d", &a, &b, &w);
60             if (!merg(a, b, w)) ans++;
61         }
62         printf("%d\n",ans);
63     }
64     return 0;
65 }