【并查集】PKU-1182 食物链

 1 #include<iostream>
 2 #include<cstdio>
 3 #include<cstdlib>
 4 #include<list>
 5 using namespace std;
 6 const int maxn = 50010;
 7 int ans;
 8 struct Animal
 9 {
10     int relative; /*relative = 0, 相对于根结点是同类；
11                     relative = 1, 相对于根结点是吃；
12                     relative = 2, 相对于根结点是被吃；*/
13     int parent;
14 }animal[maxn];
15 void MakeSet(int SizeOfSet)
16 {
17     for(int i = 0; i <= SizeOfSet; i++)
18     {
19         animal[i].parent = i;
20         animal[i].relative = 0;
21     }
22 }
23 int Find(int x)
24 {
25     int r = x;
26     if(animal[r].parent == r)   return r;
27     int tmp = animal[x].parent;
28     animal[x].parent = Find(tmp);
29     animal[x].relative = (animal[x].relative + animal[tmp].relative) % 3;
30     return animal[x].parent;
31 }
32 void Solve(int d, int x, int y, int n)
33 {
34     if((d == 2 && x == y) || x > n || y > n) {ans++; return;}
35     int rootx = Find(x), rooty = Find(y);
36     if(rootx == rooty)//结点x, y在一个集合里
37     {
38         if(d == 1)
39         {
40             if(animal[x].relative != animal[y].relative) ans++;
41         }
42         else if(d == 2)
43         {
44             if((animal[x].relative + 1) % 3 != animal[y].relative)  ans++;
45         }
46     }
47     else
48     {
49         animal[rooty].parent = rootx;
50         if(d == 1)
51         {
52             animal[rooty].relative = (animal[x].relative - animal[y].relative + 3) % 3;
53         }
54         else if(d == 2)
55         {
56             animal[rooty].relative = ((animal[x].relative + 1) % 3 - animal[y].relative + 3) % 3;
57         }
58     }
59 }
60 int main()
61 {
62     int n, k;
63     scanf("%d%d", &n, &k);
64     MakeSet(n);
65     while(k--)
66     {
67         int d, x, y;
68         scanf("%d%d%d", &d, &x, &y);
69         Solve(d, x, y, n);
70     }
71     printf("%d\n", ans);
72     return 0;
73 }