Hdu2444二分图

#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <algorithm>
#include <cmath>
#include <stack>
#include <queue>
#include <vector>
#include <map>
#include <string>
#include <iostream>
using namespace std;

int n,m;
const int maxn = 555;
int link[maxn];
int used[maxn];
int Map[maxn][maxn];
int father[maxn*2];
int getfather(int x)
{
if(father[x]!=x) father[x]=getfather(father[x]);
return father[x];
}

int dfs(int x)
{
for(int i=1;i<=n;i++){
if(Map[x][i]&&!used[i]){
used[i]=1;
if(link[i]==-1||dfs(link[i])){
link[i]= x; return 1;
}
}
}
return 0;
}

int gao()
{
int ans=0;
memset(link,-1,sizeof(link));
for(int i=1;i<=n;i++){
memset(used,0,sizeof(used));
ans+=dfs(i);
}
return ans;
}

int main()
{
int a,b;
while(cin>>n>>m){
memset(Map,0,sizeof(Map));
for(int i=1;i<=2*n;i++)
father[i]= i;
int flag=0;
for(int i=0;i<m;i++){
scanf("%d%d",&a,&b);
int fa=getfather(a);int fb= getfather(b); int fa1= getfather(a+n);int fb1= getfather(b+n);
if(fa==fb) flag=1;
father[fa]=fb1;father[fb]=fa1;
Map[a][b]=1;Map[b][a]=1;
}
if(flag){
printf("No\n");continue;
}
int t= gao();
printf("%d\n",t/2);
}
return 0;
}

#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <algorithm>
#include <cmath>
#include <stack>
#include <queue>
#include <vector>
#include <map>
#include <string>
#include <iostream>
using namespace std;

int n,m;
const int maxn = 222;
int link[maxn];
int used[maxn];
int Map[maxn][maxn];
int Dye(int x)
{
int vis[maxn];int color[maxn];
memset(vis,0,sizeof(vis));
memset(color,-1,sizeof(color));
queue<int> q;
q.push(x);
vis[x]=1; color[x]= 1;
while(!q.empty()){
int cur=q.front(); q.pop();
for(int i=1;i<=n;i++){
if(!Map[cur][i])continue;
if(color[i]==color[cur]) return 0;
color[i]=color[cur]^1;
if(!vis[i]){
vis[i]=1 ;q.push(i);
}
}
}
return 1;
}

int dfs(int x)
{
for(int i=1;i<=n;i++){
if(Map[x][i]&&!used[i]){
used[i]=1;
if(link[i]==-1||dfs(link[i])){
link[i]= x; return 1;
}
}
}
return 0;
}

int gao()
{
int ans=0;
memset(link,-1,sizeof(link));
for(int i=1;i<=n;i++){
memset(used,0,sizeof(used));
ans+=dfs(i);
}
return ans;
}

int main()
{
int a,b;
while(cin>>n>>m){
memset(Map,0,sizeof(Map));
for(int i=0;i<m;i++){
scanf("%d%d",&a,&b);
Map[a][b]=1;Map[b][a]=1;
}
int flag=0;
for(int i=1;i<=n;i++)
if(!Dye(i)) flag=1;
if(flag){
printf("No\n");continue;
}
int t= gao();
printf("%d\n",t/2);
}
return 0;
}