562

class Solution {
public:
    int longestLine(vector<vector<int>>& mat) {
        if(mat.size() == 0) return 0;
        int ans = 0, rows=mat.size(), cols=mat[0].size();
        int dp[cols][4];
        memset(dp, 0, sizeof dp);

        //0:horizontal, 1:vertical, 2:diagonal, 3:antidiagonal
        for(int i=0; i<rows; i++){
            int tmp = 0;
            for(int j=0; j<cols; j++){
                if(mat[i][j]){
                    dp[j][0] = (j>0) ? dp[j-1][0]+1 : 1;
                    dp[j][1] = (i>0) ? dp[j][1]+1 : 1;
                    int prev = dp[j][2];
                    dp[j][2] = (i>0 && j>0) ? tmp+1 : 1;
                    tmp =  prev;
                    dp[j][3] = (i>0 && j<cols-1) ? dp[j+1][3]+1 : 1;
                    ans = max({ans, dp[j][0], dp[j][1], dp[j][2], dp[j][3]});
                }
                else{
                    tmp = dp[j][2];
                    dp[j][0] = dp[j][1] = dp[j][2] = dp[j][3] = 0;
                }
            }
        }
        return ans;
    }
};