POJ2492A Bug's Life【并查集+根节点偏移】

 1 #include <iostream>
 2 #include <cstdio>
 3 #include <cstring>
 4 using namespace std;
 5 
 6 const int maxn = 2005;
 7 int fa[maxn], num[maxn];
 8 
 9 void init(int n) {
10     for(int i = 0; i <= n; i++) {
11         fa[i] = i;
12         num[i] = 0;
13     }
14 }
15 
16 int find(int i) {
17     if(i == fa[i]) {
18         return i;
19     }
20     int fi = fa[i];
21     fa[i] = find(fa[i]);
22     num[i] = (num[fi] + num[i]) % 2;
23     return fa[i];
24 }
25 
26 void unin(int u, int v) {
27     int fu = find(u); int fv = find(v);
28     if(fu != fv) {
29         fa[fv] = fu;
30         if(num[fu] == num[u]) {
31             if(num[fv] == num[v]) {
32                 num[fv] = num[fu] == 0 ? 1 : 0;
33             } else {
34                 num[fv] = num[fu] == 0 ? 0 : 1;
35             }
36         } else {
37             if(num[fv] == num[v]) {
38                 num[fv] = num[fu] == 0 ? 0 : 1;
39             } else {
40                 num[fv] = num[fu] == 0 ? 1 : 0;
41             }
42         }
43     }
44 }
45 
46 int main() {
47     int t;
48     int n, m;
49     int a, b;
50     scanf("%d",&t);
51     for(int kase = 1; kase <= t; kase++) {
52         scanf("%d %d",&n, &m);
53         init(n);
54         bool flag = false;
55         while(m--) {
56             scanf("%d %d", &a, &b);
57             if(find(a) != find(b) ) {
58                 unin(a, b);
59             } else {
60                 if(num[a] == num[b]) {
61                     flag = true;
62                 }
63             }
64         }
65         printf("Scenario #%d:\n", kase);
66         if(flag) {
67             puts("Suspicious bugs found!");
68         } else {
69             puts("No suspicious bugs found!");
70         }
71         puts("");
72     }
73     return 0;
74 }