hdoj 2444 The Accomodation of Students（裸的二分图判定+匈牙利）

#include<bits/stdc++.h>
using namespace std;
const int maxn = 205;
vector<int> e[maxn];
int match[maxn], vis[maxn], n, m;

bool judge()
{
queue<int> q;
memset(vis, -1, sizeof(vis));
q.push(1);
vis[1] = 0;
while(q.size())
{
int u = q.front();
q.pop();
for(int i = 0; i < e[u].size(); i++)
{
int to = e[u][i];
if(vis[to] == -1)
{
vis[to] = !vis[u];
q.push(to);
}
else if(vis[to] == vis[u])
return false;
}
}
return true;
}

bool Find(int x)
{
for(int i = 0; i < e[x].size(); i++)
{
int to = e[x][i];
if(!vis[to])
{
vis[to] = 1;
if(match[to] == 0 || Find(match[to]))
{
match[to] = x;
return true;
}
}
}
return false;
}

int main(void)
{
while(cin >> n >> m)
{
for(int i = 0; i < maxn; i++)
e[i].clear();
memset(match, 0, sizeof(match));
for(int i = 1; i <= m; i++)
{
int x, y;
scanf("%d%d", &x, &y);
e[x].push_back(y);
e[y].push_back(x);
}
if(!judge()) puts("No");
else
{
int ans = 0;
for(int i = 1; i <= n; i++)
{
memset(vis, 0, sizeof(vis));
ans += Find(i);
}
printf("%d\n", ans/2);
}
}
return 0;
}