Hdu2444二分图

来源：互联网发布：淘宝导航怎么全屏代码编辑：程序博客网时间：2024/06/01 09:07

给你一个图，问是否为二分图，若是求出最大匹配。

并查集判图，原理黑白染色。

#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;}

bfs判图

#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 = 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;}

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