Simple and Concise Java Solution (Easy to Understand O(m+n) space)


  • 5
    I
    public int longestLine(int[][] M) {
        if (M.length == 0 || M[0].length == 0) {
            return 0;
        }
        int max = 0;
        int[] col = new int[M[0].length];
        int[] diag = new int[M.length + M[0].length];
        int[] antiD = new int[M.length + M[0].length];
        for (int i = 0; i < M.length; i++) {
            int row = 0;
            for (int j = 0; j < M[0].length; j++) {
                if (M[i][j] == 1) {
                    row++;
                    col[j]++;
                    diag[j + i]++;
                    antiD[j - i + M.length]++;
                    max = Math.max(max, row);
                    max = Math.max(max, col[j]);
                    max = Math.max(max, diag[j + i]);
                    max = Math.max(max, antiD[j - i + M.length]);
                } else {
                    row = 0;
                    col[j] = 0;
                    diag[j + i] = 0;
                    antiD[j - i + M.length] = 0;
                }
            }
        }
        return max;
    

    }

    Btw, I realized this is very similar to N-Queens. You can use the above approach and DFS to easily tackle down N-Queens problems.


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