Reversing the columns of a Matrix

Problem Statement - link #

Given a matrix of dimensions n1 x m1. Reverse its columns in-place such that the last column will become the first column and so on.

Your Task: You dont need to read input or print anything. Complete the function reverseCol() that takes matrix as input parameter and modifies it in-place such that the last column will become the first column and so on.

Expected Time Complexity: O(n1*m1) Expected Auxiliary Space: O(1)

Examples #

Example 1:

Input:
n1 = 4, m1 = 3
matrix[][] = [[ 1,  2,  3], [ 5,  6,  7], [11, 10,  9], [13, 14, 15]]
Output: 3 2 1 7 6 5 9 10 11 15 14 13
Explanation:
Array after exchanging columns:
3 2 1
7 6 5
9 10 11
15 14 13

Example 2:

Input:
n1 = 2, m1 = 5
matrix[][] = [[ 1, 2, 3, 4, 5], [ 6, 7, 8, 9, 10]]
Output: 5 4 3 2 1 10 9 8 7 6
Explanation:
After reversing the column of matrix
 5 4 3 2 1
10 9 8 7 6

Constraints #

• 1 <= n1, m1 <= 100
• 0 <= matrixij <= 1000

Solutions #

class Solution{
    public:
    //Function to reverse the columns of a matrix.
    void reverseCol(vector<vector<int> > &matrix) {
        // code here
        int r = matrix.size(), c = matrix[0].size();
        for(int i=0; i<r; i++)
            for(int j=0; j<c/2; j++)
                swap(matrix[i][j], matrix[i][c-1-j]);
    }

};