HDU 5971 "Wrestling Match" (bipartite graph coloring)

 

Portal

 

• the meaning of problems

　　N given individual, m games;

　　This m race, the two battle in every game, part of a "good player" belonging to another "bad player";

　　Give you x number of already established "good player" and the y have been identified "bad player".

　　Q. Can I n these individuals into two categories, one of which belongs to the "good player", and the other belongs to the "bad player";

　　That there is no person that is part of "good player" and belonging to the "bad player";

　　If so, output "YES", on the contrary, the output "NO";

•answer

　　For every game of the two $ u, v $, even a two-way side $ u \ rightarrow v \, \ v \ rightarrow u $;　　

　　Then DFS staining.　　

　　Start with the already identified $ x + y $ of them began, staining associated with people, contradictions output "NO";　

　　Then for people uncertain, enumerated dyeing, contradictions output "NO";

　　If there is no contradiction, output "YES";

•Code

 1 #include<bits/stdc++.h>
 2 using namespace std;
 3 const int N=1e3+50;
 4 const int M=1e4+50;
 5 
 6 int n,m,x,y;
 7 int num;
 8 int head[N];
 9 struct Edge
10 {
11     int to;
12     int next;
13 }G[M<<1];
14 void addEdge(int u,int v)
15 {
16     G[num]={v,head[u]};
17     head[u]=num++;
18 }
19 int col[N];///0:Good , 1:bad
20 int g[N];
21 int b[N];
22 bool ok;
23 
24 void DFS(int u,int flag)
25 {
26     col[u]=flag;
27     for(int i=head[u];~i && !ok;i=G[i].next)
28     {
29         int= V G [I] .to;
 30          
31 is          IF (COL [V] == - . 1 )
 32              the DFS (V, ^ In Flag . 1 );
 33 is              
34 is          IF (COL [V] == COL [U]) /// u, v opposition, if col [u] = col [v ] appear contradictory 
35              OK = to true ;
 36      }
 37 [  }
 38 is  char * the Solve ()
 39  {
 40      for ( int I = . 1 ; I <= X; ++ I)
 41 is      {
 42 is          int U = G [I];
 43 is          OK =false;
44         if(col[u] == -1)
45             DFS(u,0);
46         if(ok || col[u] == 1)
47             return "NO";
48     }
49     for(int i=1;i <= y;++i)
50     {
51         int u=b[i];
52         if(col[u] == -1)
53             DFS(u,1);
54 
55         if(ok || col[u] == 0)
56             return "NO";
57     }
58     for(int i=1;i <= n;++i)
59     {
60         ok=false;
61         if(col[i] == -1 && head[i] != -1)
62             DFS(i,0);
63             
64         if(ok)
65             return "NO";
66     }
67     return "YES";
68 }
69 void Init()
70 {
71     num=0;
72     for(int i=0;i <= n;++i)
73     {
74         col[i]=-1;
75         head[i]=-1;
76     }
77 }
78 int main()
79 {
80 //    freopen("C:\\Users\\hyacinthLJP\\Desktop\\C++WorkSpace\\in&&out\\contest","r",stdin);
81     while(~scanf("%d%d%d%d",&n,&m,&x,&y))
82     {
83         Init();
84         for(int i=1;i <= m;++i)
85         {
86             int u,v;
87             scanf("%d%d",&u,&v);
88             addEdge(u,v);
89             addEdge(v,u);
90         }
91         for(int i=1;i <= x;++i)
92             scanf("%d",g+i);
93         for(int i=1;i <= y;++i)
94             scanf("%d",b+i);
95         puts(Solve());
96     }
97     return 0;
98 }

View Code