Rotate Image LeetCode Solution | Easy Approach

Rotate Image | 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]]

Constraints:

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

Rotate Image Solutions

✅Time:O(n2)

✅Space: O(1)

C++

class Solution {
 public:
  void rotate(vector<vector<int>>& matrix) {
    reverse(begin(matrix), end(matrix));
    for (int i = 0; i < matrix.size(); ++i)
      for (int j = i + 1; j < matrix.size(); ++j)
        swap(matrix[i][j], matrix[j][i]);
  }
};

Java

class Solution {
  public void rotate(int[][] matrix) {
    for (int i = 0, j = matrix.length - 1; i < j; ++i, --j) {
      int[] temp = matrix[i];
      matrix[i] = matrix[j];
      matrix[j] = temp;
    }

    for (int i = 0; i < matrix.length; ++i)
      for (int j = i + 1; j < matrix.length; ++j) {
        final int temp = matrix[i][j];
        matrix[i][j] = matrix[j][i];
        matrix[j][i] = temp;
      }
  }
}

Python

class Solution {
  public void rotate(int[][] matrix) {
    for (int i = 0, j = matrix.length - 1; i < j; ++i, --j) {
      int[] temp = matrix[i];
      matrix[i] = matrix[j];
      matrix[j] = temp;
    }

    for (int i = 0; i < matrix.length; ++i)
      for (int j = i + 1; j < matrix.length; ++j) {
        final int temp = matrix[i][j];
        matrix[i][j] = matrix[j][i];
        matrix[j][i] = temp;
      }
  }
}

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