Find Valid Matrix Given Row and Column Sums

You are given two arrays rowSum and colSum of non-negative integers where rowSum[i] is the sum of the elements in the i<sup>th</sup> row and colSum[j] is the sum of the elements of the j<sup>th</sup> column of a 2D matrix. In other words, you do not know the elements of the matrix, but you do know the sums of each row and column.

Find any matrix of non-negative integers of size rowSum.length x colSum.length that satisfies the rowSum and colSum requirements.

Return a 2D array representing any matrix that fulfills the requirements. It's guaranteed that at least one matrix that fulfills the requirements exists.

LeetCode Problem - 1605

class Solution {
    public int[][] restoreMatrix(int[] rowSum, int[] colSum) {
        // Get the number of rows (m) and columns (n) from the lengths of rowSum and colSum arrays
        int m = rowSum.length;
        int n = colSum.length;

        // Initialize the result matrix with dimensions m x n
        int[][] result = new int[m][n];
        int i = 0; // row index
        int j = 0; // column index

        // Loop through the matrix until we reach the end of either the rows or columns
        while (i < m && j < n) {
            // Set the current cell to the minimum of the remaining row sum or column sum
            result[i][j] = Math.min(rowSum[i], colSum[j]);
            // Subtract the value placed in the current cell from the respective row sum and column sum
            rowSum[i] -= result[i][j];
            colSum[j] -= result[i][j];

            // If the remaining row sum is zero, move to the next row
            if (rowSum[i] == 0) i++;
            // If the remaining column sum is zero, move to the next column
            if (colSum[j] == 0) j++;
        }

        // Return the restored matrix
        return result;
    }
}