gistfile1.java

class Solution {
    public int[] findDiagonalOrder(int[][] matrix) {
        
        if (matrix.length == 0) {
            return new int[0];
        }
        
        int m = matrix.length, n = matrix[0].length;
        int[] result = new int[m*n];
        
        int[][] direction = {{-1, 1}, {1, -1}};
        int d = 0, j = 0, row = 0, col = 0, rightBound = n - 1, bottomBound = m - 1;
        
        while (j < m * n) {
            
            result[j++] = matrix[row][col];
            
            if (d == 0) {
                if (row == 0 || col == rightBound) {
                    d = 1;
                }
                if (row == 0 && col == rightBound) {
                    row += 1;
                    continue;
                } else if (row == 0) {
                    col += 1;
                    continue;
                } else if (col == rightBound) {
                    row += 1;
                    continue;
                }
            } else if (d == 1) {
                if (col == 0 || row == bottomBound) {
                    d = 0;
                }
                if (col == 0 && row == bottomBound) {
                    col += 1;
                    continue;
                } else if (col == 0) {
                    row += 1;
                    continue;
                } else if (row == bottomBound) {
                    col += 1;
                    continue;
                }
            }
            
            row += direction[d][0];
            col += direction[d][1];
        }
        
        return result;
    }
}