hdu 5971 Wrestling Match

题意：N个选手，M场比赛，已知x个好人，y个坏人，问能否将选手划分成好人和坏人两个阵营，保证每场比赛必有一个好人和一个坏人参加。

题解：dfs染色。听说题意模糊？从样例来看，第一个例子应该是因为2可能是好人可能是坏人，所以不确定就NO了...

 1 #include <iostream>
 2 #include <cstring>
 3 #include <cstdio>
 4 #include <algorithm>
 5 #include <cmath>
 6 #include <vector>
 7 #define CLR(a,b) memset((a),(b),sizeof((a)))
 8 using namespace std;
 9 typedef long long ll;
10 const int N = 1005;
11 const int inf = 0x3f3f3f3f;
12 int n, m , x, y, flag;
13 vector<int> g[N];
14 int vis[N];
15 void dfs(int u) {
16     int f = 0;
17     if(vis[u]==-1) {vis[u] = 0;f = 1;}
18     for(int i = 0; i < g[u].size(); ++i) {
19         int v = g[u][i];
20         if(vis[v]==vis[u] && f==1) {f=2; vis[u] = 1-vis[v];}
21         if(vis[v]==vis[u]) flag = 0;
22         if(vis[v]==-1) {vis[v] = 1-vis[u]; dfs(v);}
23     }
24 }
25 int main() {
26     int i, j, t, u, v;
27     while(~scanf("%d%d%d%d", &n, &m, &x, &y)) {
28         for(i = 1; i <= n; ++i) g[i].clear();
29         CLR(vis, -1); flag = 1;
30         while(m--) {
31             scanf("%d%d", &u, &v);
32             g[u].push_back(v);
33             g[v].push_back(u);
34         }
35         while(x--) {
36             scanf("%d", &u);
37             vis[u] = 0;
38         }
39         while(y--) {
40             scanf("%d", &v);
41             vis[v] = 1;
42         }
43         for(i = 1; i <= n; ++i){
44             if(g[i].size()) dfs(i);
45         }
46         for(i = 1; i <= n; ++i)if(vis[i]==-1){flag = 0;break;}
47         if(flag) puts("YES");
48         else puts("NO");
49     }
50     return 0;
51 }

62ms