Rotate image - Leetcode 48 - first reverse up to down, and then swap the symmetry. Pass online judge.

RotateImage_leetcode48_Practice.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace RotateImage_SimpleOne
{
    /// <summary>
    /// study the rotate image - Leetcode discussion
    /// https://leetcode.com/problems/rotate-image/#/description
    /// 
    /// </summary>
    class Program
    {
        static void Main(string[] args)
        {
        }

        /*
         * clockwise rotate
         * first reverse up to down, then swap the symmetry 
         * 1 2 3     7 8 9     7 4 1
         * 4 5 6  => 4 5 6  => 8 5 2
         * 7 8 9     1 2 3     9 6 3
        */
        private static void rotate(int[,] matrix) {
            int rows = matrix.GetLength(0); 
            int cols = matrix.GetLength(1); 
            
            int index = 0;
            while (2 * index < rows )
            {
                reverseRows(index, rows -1 - index, matrix);
                index++; 
            }

            for (int row = 0; row < rows; ++row) 
            {
                for (int col = row + 1; col < cols; ++col)
                {
                    swap(row, col, matrix);
                }
            }
        }

        private static void reverseRows(int row1, int row2, int[,] matrix)
        {
            int cols = matrix.GetLength(1);
            for (int col = 0; col < cols; col++)
            {
                int tmp = matrix[row1, col];
                matrix[row1, col] = matrix[row2, col];
                matrix[row2, col] = tmp; 
            }
        }

        private static void swap(int row, int col, int[,] matrix)
        {
            int tmp = matrix[row, col];
            matrix[row, col] = matrix[col, row];
            matrix[col, row] = tmp; 
        }

        /*
         * anticlockwise rotate
         * first reverse left to right, then swap the symmetry
         * 1 2 3     3 2 1     3 6 9
         * 4 5 6  => 6 5 4  => 2 5 8
         * 7 8 9     9 8 7     1 4 7
        */
        void anti_rotate(int[,] matrix) {
            int rows = matrix.GetLength(0);
            int cols = matrix.GetLength(1);
            
            reverseTwoCols(0, cols - 1, matrix);

            for (int row = 0; row < rows; ++row)
            {
                for (int col = row + 1; col < cols; ++col)
                {
                    swap(row, col, matrix);
                }
            }
        } 
   
        private static void reverseTwoCols(int row, int col, int[,] matrix)
        {
        }

        public void Rotate(int[,] matrix) {
        
        }
    }
}