Wave Print

vector<int> wavePrint(vector<vector<int> > arr, int nRows, int mCols)
{
    vector<int> ans;
    // Loop through each column
    for(int col=0; col<mCols; col++) {
        // If the column index is odd, traverse bottom-to-top
        if(col & 1) {
            // Odd Index -> Bottom to top
            for(int row = nRows-1; row >= 0; row--) {
                ans.push_back(arr[row][col]);
            }
        }
        // If the column index is even, traverse top-to-bottom
        else {
            // 0 or even index -> Top to bottom
            for(int row = 0; row < nRows; row++) {
                ans.push_back(arr[row][col]);
            }
        }
    }
    return ans;
}

Example:

vector<vector<int>> arr = {{1, 2, 3},
                           {4, 5, 6},
                           {7, 8, 9}};

int nRows = 3, mCols = 3;
vector<int> result = wavePrint(arr, nRows, mCols);

Step-by-Step Example:

Given the matrix:

1  2  3
4  5  6
7  8  9

• Iteration 1 (Column 0, even index):
  • Traverse top to bottom: 1, 4, 7.
  • ans = {1, 4, 7}.
• Iteration 2 (Column 1, odd index):
  • Traverse bottom to top: 8, 5, 2.
  • ans = {1, 4, 7, 8, 5, 2}.
• Iteration 3 (Column 2, even index):
  • Traverse top to bottom: 3, 6, 9.
  • ans = {1, 4, 7, 8, 5, 2, 3, 6, 9}.

Thus, the wave print of the matrix is: [1, 4, 7, 8, 5, 2, 3, 6, 9].