URAL1099 Work Scheduling（一般图匹配）

#include <iostream>
#include <cstdio>
#include <queue>
#include <string.h>
#define SET(a,b) memset(a,b,sizeof(a));
using namespace std;

const int MAX=230;
queue<int> Q;
int g[MAX][MAX],inque[MAX],inblossom[MAX];
int match[MAX],pre[MAX],set[MAX];
int n;

int findancestor(int u,int v)
{
int visit[MAX]={0};
while(1)
{
u=set[u];
visit[u]=1;
if(match[u]==-1) break;
u=pre[match[u]];
}
while(1)
{
v=set[v];
if(visit[v]) break;
v=pre[match[v]];
}
return v;
}

void reset(int u,int root)
{
int v;
while(u!=root)
{
v=match[u];
inblossom[set[u]]=1;
inblossom[set[v]]=1;
v=pre[v];
if(set[v]!=root) pre[v]=match[u];
u=v;
}
}

void contract(int u,int v)
{
int root=findancestor(u,v);
int i;
SET(inblossom,0);
reset(u,root);
reset(v,root);
if(set[u]!=root) pre[u]=v;
if(set[v]!=root) pre[v]=u;
for(i=1;i<=n;i++) if(inblossom[set[i]])
{
set[i]=root;
if(!inque[i]) Q.push(i),inque[i]=1;
}
}

int BFS(int S)
{
int u,v,i,t;
for(i=1;i<=n;i++)pre[i]=-1,inque[i]=0,set[i]=i;
while(!Q.empty()) Q.pop();
Q.push(S);
inque[S]=1;
while(!Q.empty())
{
u=Q.front();
Q.pop();
for(v=1;v<=n;v++)if(g[u][v]&&set[v]!=set[u]&&match[u]!=v)
{
if(v==S||match[v]!=-1&&pre[match[v]]!=-1) contract(u,v);
else if(pre[v]==-1)
{
pre[v]=u;
if(match[v]!=-1)
{
Q.push(match[v]);
inque[match[v]]=1;
}
else
{
u=v;
while(u!=-1)
{
v=pre[u];
t=match[v];
match[u]=v;
match[v]=u;
u=t;
}
return 1;
}
}
}
}
return 0;
}

int solve()
{
SET(match,-1);
int i,ans=0;
for(i=1;i<=n;i++) if(match[i]==-1&&BFS(i)) ans++;
return ans;
}

int main()
{
while(scanf("%d",&n)!=-1)
{
int i,u,v;
SET(g,0);
while(scanf("%d%d",&u,&v)!=-1)g[u][v]=g[v][u]=1;
printf("%d\n",solve()*2);
int visit[MAX];
SET(visit,0);
for(i=1;i<=n;i++) if(!visit[i]&&match[i]!=-1)
{
printf("%d %d\n",i,match[i]);
visit[i]=visit[match[i]]=1;
}
}
return 0;
}