No.145 - LeetCode1284 - 状压BFS - 黑白棋

class Solution {
public:
    int getStatus(int loc,int status,int N,int M){
        status ^= (1<<loc);
        // 非矩阵右边届
        if(loc % M != 0) status ^= (1<<(loc-1));
        // 非矩阵左边界
        if((loc+1) % M != 0) status ^= (1<<(loc+1));
        // 非矩阵上边界
        if(loc/M < N-1) status ^= (1<<(loc+M));
        // 非矩阵下边界
        if(loc/M > 0) status ^= (1<<(loc-M));
        return status;
    }
    int minFlips(vector<vector<int>>& mat) {
        int N = mat.size();
        int M = mat[0].size();
        queue<int> q;
        int status = 0;
        for(int i=0;i<N;i++){
            for(int j=0;j<M;j++){
                status<<=1;
                if(mat[i][j] == 1) status++;
            }
        }
        if(status == 0) return 0;
        map<int,int> mp;
        q.push(status);
        mp[status] = 1;
        while(!q.empty()){
            int now = q.front();
            //printf("<%d %d>\n",now,mp[now]-1);
            q.pop();
            for(int i=0;i<N*M;i++){
                int newstatus = getStatus(i,now,N,M);
                if(newstatus == 0) return mp[now];
                if(mp[newstatus] == 0){
                    q.push(newstatus);
                    mp[newstatus] = mp[now]+1;
                }
            }
        }
        return -1;
    }
};