hdu 4751 Divide Groups(dfs染色 或 2-sat)

 1 #pragma comment(linker, "/STACK:1024000000,1024000000")
 2 #include<iostream>
 3 #include<cstdio>
 4 #include<cstring>
 5 #include<cmath>
 6 #include<math.h>
 7 #include<algorithm>
 8 #include<queue>
 9 #include<set>
10 #include<bitset>
11 #include<map>
12 #include<vector>
13 #include<stdlib.h>
14 using namespace std;
15 #define ll long long
16 #define eps 1e-10
17 #define MOD 1000000007
18 #define N 106
19 #define inf 1e12
20 int n;
21 vector<int>v[N];
22 int color[N];
23 int mp[N][N];
24 bool dfs(int u,int c){
25     color[u]=c;
26     for(int i=0;i<v[u].size();i++){
27         int num=v[u][i];
28         if(color[num]!=-1){
29             if(color[num]==c){
30                 return false;
31             }
32             continue;
33         }
34         if(!dfs(num,!c)) return false;
35     }
36     return true;
37 }
38 int main()
39 {
40     while(scanf("%d",&n)==1){
41         for(int i=0;i<N;i++){
42             v[i].clear();
43         }
44         memset(mp,0,sizeof(mp));
45         for(int i=1;i<=n;i++){
46             int x;
47             scanf("%d",&x);
48             while(x!=0){
49                 //v[i].push_back(x);
50                 //v[x].push_back(i);
51                 mp[i][x]=1;
52                 scanf("%d",&x);
53             }
54         }
55         
56         for(int i=1;i<=n;i++){
57             for(int j=i+1;j<=n;j++){
58                 if(mp[i][j]==0 || mp[j][i]==0){
59                     v[i].push_back(j);
60                     v[j].push_back(i);
61                 }
62             }
63         }
64         
65         memset(color,-1,sizeof(color));
66         int flag=1;
67         for(int i=1;i<=n;i++){
68             if(color[i]==-1 && !dfs(i,0)){
69                 flag=0;
70                 break;
71             }
72         }
73         if(flag){
74             printf("YES\n");
75         }
76         else{
77             printf("NO\n");
78         }
79     }
80     return 0;
81 }

  1 #pragma comment(linker, "/STACK:1024000000,1024000000")
  2 #include<iostream>
  3 #include<cstdio>
  4 #include<cstring>
  5 #include<cmath>
  6 #include<math.h>
  7 #include<algorithm>
  8 #include<queue>
  9 #include<set>
 10 #include<bitset>
 11 #include<map>
 12 #include<vector>
 13 #include<stdlib.h>
 14 #include <stack>
 15 using namespace std;
 16 #define PI acos(-1.0)
 17 #define max(a,b) (a) > (b) ? (a) : (b)  
 18 #define min(a,b) (a) < (b) ? (a) : (b)
 19 #define ll long long
 20 #define eps 1e-10
 21 #define MOD 1000000007
 22 #define N 106
 23 #define inf 1e12
 24 int n,m;
 25 
 26 int mp[N][N];
 27 int tot;
 28 int head[N];
 29 int vis[N];
 30 int tt;
 31 int scc;
 32 stack<int>s;
 33 int dfn[N],low[N];
 34 int col[N];
 35 struct Node
 36 {
 37     int from;
 38     int to;
 39     int next;
 40 }edge[N*N];
 41 void init()
 42 {
 43     tot=0;
 44     scc=0;
 45     tt=0;
 46     memset(head,-1,sizeof(head));
 47     memset(dfn,-1,sizeof(dfn));
 48     memset(low,0,sizeof(low));
 49     memset(vis,0,sizeof(vis));
 50     memset(col,0,sizeof(col));
 51 }
 52 void add(int s,int u)//邻接矩阵函数
 53 {
 54     edge[tot].from=s;
 55     edge[tot].to=u;
 56     edge[tot].next=head[s];
 57     head[s]=tot++;
 58 }
 59 void tarjan(int u)//tarjan算法找出图中的所有强连通分支
 60 {
 61     dfn[u] = low[u]= ++tt;
 62     vis[u]=1;
 63     s.push(u);
 64     int cnt=0;
 65     for(int i=head[u];i!=-1;i=edge[i].next)
 66     {
 67         int v=edge[i].to;
 68         if(dfn[v]==-1)
 69         {
 70         //    sum++;
 71             tarjan(v);
 72             low[u]=min(low[u],low[v]);
 73         }
 74         else if(vis[v]==1)
 75           low[u]=min(low[u],dfn[v]);
 76     }
 77     if(dfn[u]==low[u])
 78     {
 79         int x;
 80         scc++;
 81         do{
 82             x=s.top();
 83             s.pop();
 84             col[x]=scc;
 85             vis[x]=0;
 86         }while(x!=u);
 87     }
 88 }
 89 bool two_sat(){
 90     
 91     for(int i=0;i<2*n;i++){
 92         if(dfn[i]==-1){
 93             tarjan(i);
 94         }
 95     }
 96     for(int i=0;i<n;i++){
 97         if(col[2*i]==col[2*i+1]){
 98             return false;
 99         }
100     }
101     return true;
102 }
103 int main()
104 {
105     while(scanf("%d",&n)==1){
106          init();
107          memset(mp,0,sizeof(mp));
108          
109          while(!s.empty()){
110              s.pop();
111          }
112         int a,b,c;
113         int x;
114        for(int i=0;i<n;i++){
115               scanf("%d",&x);
116               while(x!=0){
117                   x--;
118                   mp[i][x]=1;
119                   scanf("%d",&x);
120             }
121         }
122         for(int i=0;i<n;i++){
123               for(int j=0;j<n;j++){
124                   if(i==j) continue;
125                   if(mp[i][j]==0){
126                   add(2*i,2*j+1);
127               add(2*j,2*i+1);
128               add(2*i+1,2*j);
129               add(2*j+1,2*i);
130                  }
131             }
132         }
133         if(two_sat()){
134             printf("YES\n");
135         }
136         else{
137             printf("NO\n");
138         }
139     }
140     return 0;
141 }