Spiral array - practice 2017 May

spiralArray_practice2017May.cs

using System;

class Solution
{
    // Spiral array - 
    public static void Main()
    {
        var testcase = new int[4][];
        testcase[0] = new int[] {1, 2, 3, 4 };
        testcase[1] = new int[] {12, 13, 14, 5 };
        testcase[2] = new int[] {11, 16, 15, 6 };
        testcase[3] = new int[] {10, 9, 8, 7 };

        testcase = new int[1][];
        testcase[0] = new int[] { 1 }; 

        var result = SpiralCopy(testcase); 
    }

    public static int[] SpiralCopy(int[][] matrix)
    {        
        int rows = matrix.Length;
        int cols = matrix[0].Length;

        int total = rows * cols;
        var spiral = new int[total];        

        int index = 0;

        int leftCol = 0;
        int rightCol = cols - 1;
        int topRow = 0;
        int bottomRow = rows - 1;

        // the idea is to simplify the while loop - one variable checking, check the length of spiral 
        // array intead of compared to the start position of spiral layer. 
        while (index < total)
        {
            // top row - go right, 
            for (int col = leftCol; col <= rightCol; col++)
            {
                var current = matrix[topRow][col];
                spiral[index++] = current;
            }

            // right col - go down
            for (int row = topRow + 1; row <= bottomRow; row++)
            {
                var current = matrix[row][rightCol];
                spiral[index++] = current;
            }

            // go left
            for (int col = rightCol - 1; col >= leftCol; col--)
            {
                var current = matrix[bottomRow][col];
                spiral[index++] = current;
            }

            // go up 
            for (int row = bottomRow - 1; row > topRow; row--)
            {
                var current = matrix[row][leftCol];
                spiral[index++] = current;                
            }

            leftCol++;
            rightCol--;
            topRow++;
            bottomRow--;
        }

        return spiral;
    }
}

Julia noticed that there are a bug line 53 - line 58. The array index out-of-range error. One row is the special test case, need to check if(topRow == bottomRow), and also one column checking before left col handling from line 60 - line 65.