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by Sumit Chourasia | Oct 26, 2020 | Category :coding | Tags : algorithm array data-structure leetcode medium

Rotate Image - Array - Medium - LeetCode

Rotate Image - Array - Medium - LeetCode

You are given an n x n 2D matrix representing an image, rotate the image by 90 degrees (clockwise).

You have to rotate the image in-place, which means you have to modify the input 2D matrix directly. DO NOT allocate another 2D matrix and do the rotation.

 

Example 1:


Input: matrix = [[1,2,3],[4,5,6],[7,8,9]]
Output: [[7,4,1],[8,5,2],[9,6,3]]
Example 2:


Input: matrix = [[5,1,9,11],[2,4,8,10],[13,3,6,7],[15,14,12,16]]
Output: [[15,13,2,5],[14,3,4,1],[12,6,8,9],[16,7,10,11]]
Example 3:

Input: matrix = [[1]]
Output: [[1]]
Example 4:

Input: matrix = [[1,2],[3,4]]
Output: [[3,1],[4,2]]
 

Constraints:

matrix.length == n
matrix[i].length == n
1 <= n <= 20
-1000 <= matrix[i][j] <= 1000

 

public class Solution {
    public void Rotate(int[][] matrix) {
        if(matrix.Length==0){
            return;
        }
        
        int s = 0;
        int e = matrix.Length-1;
        while(s < e){
            var temp = matrix[s];
            matrix[s]=matrix[e];
            matrix[e]=temp;
            s++;
            e--;
        }
        
        for(int i=0; i< matrix.Length;i++){
            for(int j=i+1;j<matrix.Length;j++){
                int temp = matrix[i][j];
                matrix[i][j]=matrix[j][i];
                matrix[j][i]=temp;
            }
        }
    }
}

Time Complexity: O(m*n)

Space Complexity: O(1)

 

Where m and n are rows and columns of matrix.