链接：https://www.luogu.org/problemnew/show/P2024
思路：种类并查集，捣鼓捣鼓把题A了，但是没咋懂，列入学习清单，参考了这篇博客和这篇博客
代码：
1 //#include<bits/stdc++.h> 2 #include<iostream> 3 #include<vector> 4 #include<stack> 5 #include<string> 6 #include<cstdio> 7 #include<algorithm> 8 #include<queue> 9 #include<map> 10 #include<set> 11 #include<cmath> 12 #define inf 0x3f3f3f3f 13 using namespace std; 14 typedef long long ll; 15 const int M = int(1e5) * 3 + 5; 16 struct node 17 { 18 int id; 19 int re;//0同类，1吃，2被吃 20 }root[M]; 21 void init(int n) 22 { 23 for (int i = 0; i <= n; i++) 24 { 25 root[i].id = i; 26 root[i].re = 0; 27 } 28 } 29 int Find(int x) 30 { 31 /*if (x != root[x].id) 32 { 33 root[x].re = (Find(root[x].re) + root[x].re) % 3; 34 root[x].id = Find(root[x].id); 35 } 36 return root[x].id;*/ 37 if (x == root[x].id) return x; 38 int temp = root[x].id; 39 root[x].id = Find(temp); 40 root[x].re = (root[x].re + root[temp].re) % 3; 41 return root[x].id; 42 } 43 //void merge(int x, int y) 44 //{ 45 // x = Find(x); 46 // y = Find(y); 47 // if (x != y) root[x].id = y; 48 //} 49 signed main() 50 { 51 int n, k; 52 cin >> n >> k; 53 init(n); 54 int sum = 0; 55 for (int i = 0; i < k; i++) 56 { 57 int op, x, y; 58 cin >> op >> x >> y; 59 if (x > n || y > n) 60 { 61 sum++; 62 continue; 63 } 64 if (op == 2 && x == y) 65 { 66 sum++; 67 continue; 68 } 69 int xx = Find(x); 70 int yy = Find(y); 71 if (xx != yy) 72 { 73 root[yy].id = xx; 74 root[yy].re = (3 - root[y].re + op - 1 + root[x].re) % 3; 75 } 76 else 77 { 78 if (op == 1 && root[x].re != root[y].re) 79 { 80 sum++; 81 continue; 82 } 83 if (op == 2 && (3 - root[x].re + root[y].re) % 3 != op - 1) 84 { 85 sum++; 86 continue; 87 } 88 } 89 } 90 cout << sum << endl; 91 return 0; 92 }
备注：关键是关系域的更新的公式，用向量的方式去思考会更好理解一点