POJ1182 食物链 —— 带权并查集

 1 #include <iostream>
 2 #include <cstdio>
 3 #include <cstring>
 4 #include <cmath>
 5 #include <algorithm>
 6 #include <vector>
 7 #include <queue>
 8 #include <stack>
 9 #include <map>
10 #include <string>
11 #include <set>
12 #define ms(a,b) memset((a),(b),sizeof((a)))
13 using namespace std;
14 typedef long long LL;
15 const double EPS = 1e-8;
16 const int INF = 2e9;
17 const LL LNF = 2e18;
18 const int MAXN = 5e4+10;
19 
20 int n, m;
21 int fa[MAXN], r[MAXN];
22 
23 int find(int x)
24 {
25     if(fa[x]==-1) return x;
26     int pre = find(fa[x]);
27     r[x] = (r[x]+r[fa[x]])%3;
28     return fa[x] = pre;
29 }
30 
31 bool Union(int w, int u, int v)
32 {
33     int fu = find(u);
34     int fv = find(v);
35     if(fu==fv)
36         return ((3-w+r[u])%3!=r[v]);
37 
38     fa[fu] = fv;
39     r[fu] = (3-r[u]+w+r[v])%3;
40     return false;
41 }
42 
43 int main()
44 {
45     scanf("%d%d", &n, &m);
46     memset(r, 0, sizeof(r));
47     memset(fa, -1, sizeof(fa));
48 
49     int ans = 0;
50     for(int i = 1; i<=m; i++)
51     {
52         int d, u, v;
53         scanf("%d%d%d", &d, &u, &v);
54         if(u>n || v>n)
55             ans++;
56         else if(d==2 && u==v)
57             ans++;
58         else if(Union(d-1, u, v))
59             ans++;
60     }
61     printf("%d\n", ans);
62 }