valid matrix.cpp

class Solution {
public:
    vector<vector<int>> restoreMatrix(vector<int>& rowSum, vector<int>& colSum) {
        int rows = rowSum.size();
        int cols = colSum.size();
        int cur_row = 0, cur_col = 0;
        vector<vector<int>> res(rows, vector<int>(cols, 0));

        while (cur_row < rows || cur_col < cols) {
            if (cur_row >= rows) {
                res[rows - 1][cur_col] = colSum[cur_col];
                cur_col++;
                continue;
            } else if (cur_col >= cols) {
                res[cur_row][cols - 1] = rowSum[cur_row];
                cur_row++;
                continue;
            }

            int value_to_put = min(rowSum[cur_row], colSum[cur_col]);
            rowSum[cur_row] -= value_to_put;
            colSum[cur_col] -= value_to_put;
            res[cur_row][cur_col] = value_to_put;

            // I write this as this because it's possible that rowSum[cur_row] == colSum[cur_col] and we'll want to move both row and col pointers
            if (rowSum[cur_row] == 0) {
                cur_row++;
            }
            if (colSum[cur_col] == 0) {
                cur_col++;
            }
        }
        return res;
    }
};