leetcode 1066. 校园自行车分配 II

题目链接

 Code:

class Solution {
public:
    int sub;
    int assignBikes(vector<vector<int>>& workers, vector<vector<int>>& bikes) {
        int N=workers.size();
        int M=bikes.size();
        vector<vector<int>> dis(N,vector<int>(M,0));
        vector<int> expw(N,INT_MIN);
        vector<int> expb(M,0);
        for(int i=0;i<N;++i){
            for(int j=0;j<M;++j){
                dis[i][j]=-(abs(workers[i][0]-bikes[j][0])+abs(workers[i][1]-bikes[j][1]));
                expw[i]=max(expw[i],dis[i][j]);
            }
        }
        vector<int> bmat(M,-1);

        for(int i=0;i<N;++i){
            while(true){
                vector<bool> wvisit(N,false);
                vector<bool> bvisit(M,false);
                sub=INT_MAX;
                if(dfs(i,wvisit,bvisit,dis,expw,expb,bmat)){
                    break;
                }
                
                for(int j=0;j<N;++j){
                    if(wvisit[j]){
                        expw[j]-=sub;
                    }
                }
                for(int j=0;j<M;++j){
                    if(bvisit[j]){
                        expb[j]+=sub;
                    }
                }
            }
        }

        int res=0;
        for(int i=0;i<M;++i){
            if(bmat[i]!=-1){
                res+=dis[bmat[i]][i];
            }
        }
        return -res;
    }

    bool dfs(int w, vector<bool> &wvisit, vector<bool> &bvisit,
        vector<vector<int>> &dis, vector<int> &expw, vector<int> &expb, vector<int> &bmat){
            wvisit[w]=true;
            for(int i=0;i<dis[0].size();++i){
                if(bvisit[i]) continue;
                int diff=expw[w]+expb[i]-dis[w][i];
                if(diff==0){
                    bvisit[i]=true;
                    if(bmat[i]==-1 || dfs(bmat[i],wvisit,bvisit,dis,expw,expb,bmat)){
                        bmat[i]=w;
                        return true;
                    }
                }else{
                    sub=min(sub,diff);
                }
            }
            return false;
        }
};