HDU-4751 Divide Groups 染色问题
题目链接：http://acm.hdu.edu.cn/showproblem.php?pid=4751
题意：有n个人，每个人都认识一些人，要求把他们分成两个集合，使得两个集合中的人都相符两两认识。
如果两个人单向认识或者相互不认识，那么必定在不同的集合，因此建立边，染色就可以了。。
1 //STATUS:C++_AC_31MS_388KB 2 #include <functional> 3 #include <algorithm> 4 #include <iostream> 5 //#include <ext/rope> 6 #include <fstream> 7 #include <sstream> 8 #include <iomanip> 9 #include <numeric> 10 #include <cstring> 11 #include <cassert> 12 #include <cstdio> 13 #include <string> 14 #include <vector> 15 #include <bitset> 16 #include <queue> 17 #include <stack> 18 #include <cmath> 19 #include <ctime> 20 #include <list> 21 #include <set> 22 #include <map> 23 using namespace std; 24 #pragma comment(linker,"/STACK:102400000,102400000") 25 //using namespace __gnu_cxx; 26 //define 27 #define pii pair<int,int> 28 #define mem(a,b) memset(a,b,sizeof(a)) 29 #define lson l,mid,rt<<1 30 #define rson mid+1,r,rt<<1|1 31 #define PI acos(-1.0) 32 //typedef 33 typedef __int64 LL; 34 typedef unsigned __int64 ULL; 35 //const 36 const int N=110; 37 const int INF=0x3f3f3f3f; 38 const int MOD=9973,STA=8000010; 39 const LL LNF=1LL<<60; 40 const double EPS=1e-6; 41 const double OO=1e60; 42 const int dx[4]={-1,0,1,0}; 43 const int dy[4]={0,1,0,-1}; 44 const int day[13]={0,31,28,31,30,31,30,31,31,30,31,30,31}; 45 //Daily Use ... 46 inline int sign(double x){return (x>EPS)-(x<-EPS);} 47 template<class T> T gcd(T a,T b){return b?gcd(b,a%b):a;} 48 template<class T> T lcm(T a,T b){return a/gcd(a,b)*b;} 49 template<class T> inline T lcm(T a,T b,T d){return a/d*b;} 50 template<class T> inline T Min(T a,T b){return a<b?a:b;} 51 template<class T> inline T Max(T a,T b){return a>b?a:b;} 52 template<class T> inline T Min(T a,T b,T c){return min(min(a, b),c);} 53 template<class T> inline T Max(T a,T b,T c){return max(max(a, b),c);} 54 template<class T> inline T Min(T a,T b,T c,T d){return min(min(a, b),min(c,d));} 55 template<class T> inline T Max(T a,T b,T c,T d){return max(max(a, b),max(c,d));} 56 //End 57 58 int n; 59 int g[N][N],color[N]; 60 vector<int> G[N]; 61 62 bool bipartite(int u) 63 { 64 for(int i=0;i<G[u].size();i++){ 65 int v=G[u][i]; 66 if(color[v]==color[u])return false; 67 if(!color[v]){ 68 color[v]=3-color[u]; 69 if(!bipartite(v))return false; 70 } 71 } 72 return true; 73 } 74 75 int main(){ 76 // freopen("in.txt","r",stdin); 77 int i,j,a,b; 78 while(~scanf("%d",&n)) 79 { 80 mem(g,0); 81 for(i=1;i<=n;i++)G[i].clear(); 82 for(i=1;i<=n;i++){ 83 while(scanf("%d",&a) && a)g[i][a]=1; 84 } 85 for(i=1;i<=n;i++){ 86 for(j=i+1;j<=n;j++){ 87 if( (!g[i][j]&&g[j][i]) || (g[i][j]&&!g[j][i]) || (!g[i][j]&&!g[j][i])) { 88 G[i].push_back(j); 89 G[j].push_back(i); 90 } 91 } 92 } 93 94 mem(color,0); 95 int ok=1; 96 for(i=1;i<=n;i++){ 97 if(!color[i]){ 98 color[i]=1; 99 if(!bipartite(i)){ 100 ok=0; 101 break; 102 } 103 } 104 } 105 106 printf("%s\n",ok?"YES":"NO"); 107 } 108 return 0; 109 }
