棋盘问题（二分图最大匹配+暴力寻找重要点）

先寻找二分图最大匹配

然后根据最大匹配来判断匹配中的每个点是否是重要点（即删掉这个点匹配数是否变少）

暴力循环判断一遍即可

#include<iostream>
#include<cstdio>
#include<string.h>
#include<vector>
using namespace std;
const int maxn = 105;
int used[maxn];
int linker[maxn];
vector<int>v[maxn];
int mp[105][105];
int n,m,k;
void init(){

    memset(mp,0,sizeof(mp));
}
bool dfs(int u){
    for(int i =1;i<=m;++i){
            int to = i;
        if(!used[to]&&mp[u][to]){
            used[to]=1;
            if(linker[to]==-1||dfs(linker[to])){
                linker[to] = u;
                return true;
            }
        }
    }
    return false;
}
int hungry(){
    memset(linker,-1,sizeof(linker));
    int res = 0;
    for(int i =1;i<=n;++i){
        memset(used,0,sizeof(used));
        if(dfs(i))
            res++;
    }
    return res;
}
int main(){
    int ca = 1;
    while(~scanf("%d%d%d",&n,&m,&k)){
        int x,y;
        init();
        for(int i =0;i<k;++i){
            scanf("%d%d",&x,&y);
            mp[x][y]=1;
        }

        int maxs = hungry();
        int sum = 0;
        int sum1 = 0;//improtant
        int lin[200];
        for(int i =1;i<=m;++i){
            lin[i] = linker[i];
        }
        for(int i=1;i<=m;++i){
            if(lin[i]!=-1){
                sum++;
                int from = lin[i];
                mp[from][i]=0;
                int temp = hungry();
                mp[from][i]=1;
                if(temp!=maxs)
                    sum1++;
            }
        }

        printf("Board %d have %d important blanks for %d chessmen.\n",ca++,sum1,sum);



    }

}