思路：裸的匈牙利算法模板。这位大佬写的简单易懂，可以参考一下二分图匹配问题。https://blog.csdn.net/dark_scope/article/details/8880547

 

#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
const int maxn = 105;
int graph[maxn][maxn];
int used[maxn];
int match[maxn];
int n,m;
int solve(int x)
{
    for(int i = 0;i < m;i++)
    {
        if(graph[x][i]&&!used[i])
        {
            used[i] = 1;
            if(match[i]==-1||solve(match[i])>0)
            {
                match[i] = x;
                return 1;
            }
        }
    }
    return 0;
}
int main()
{
    int ans = 0;
    cin>>n>>m;
    int a,b;
    while(cin>>a>>b)
    {
        if(a == -1||b == -1) break;
        graph[a-1][b-1] = 1;
    }
    memset(match,-1,sizeof(match));
    for(int i = 0;i < n;i++)
    {
        memset(used,0,sizeof(used));
        if(solve(i)) ans++;
    }
    if(ans > 0)cout<<ans<<endl;
    else cout<<"No Solution!"<<endl;
    return 0;
}