Puzzle Solver

You are tasked to solve a simple numeric puzzle. You have a 2D grid of size n x n filled with numbers from 1 to n and 0 representing empty spaces. Your goal is to fill in the empty spaces such that each number from 1 to n appears exactly once in each row and each column. If no solution is possible, return "No solution". Input Format: - The first line contains the integer `n` (1 ≤ n ≤ 9). - The next n lines each contain n integers where 0 represents an empty space. Output Format: - Print the filled grid row-wise if a solution exists. If no solution exists, print "No solution". Example: Input: 3 1 0 3 0 2 0 0 0 1 Output: 1 2 3 3 2 1 2 1 3