Added Solution - GfG to GitHub

Difficulty: Hard/Solve the Sudoku/solve-the-sudoku.cpp

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+//{ Driver Code Starts
+#include <bits/stdc++.h>
+using namespace std;
+
+
+// } Driver Code Ends
+class Solution {
+  public:
+
+// Helper function to check if a number can be placed in a cell
+bool isSafe(vector<vector<int>>& mat, int row, int col, int num) {
+    // Check row and column
+    for (int i = 0; i < 9; i++) {
+        if (mat[row][i] == num || mat[i][col] == num) {
+            return false;
+        }
+    }
+
+    // Check 3x3 sub-grid
+    int startRow = row - row % 3;
+    int startCol = col - col % 3;
+    for (int i = 0; i < 3; i++) {
+        for (int j = 0; j < 3; j++) {
+            if (mat[startRow + i][startCol + j] == num) {
+                return false;
+            }
+        }
+    }
+
+    return true;
+}
+
+// Recursive function to solve the Sudoku
+bool solve(vector<vector<int>>& mat) {
+    for (int row = 0; row < 9; row++) {
+        for (int col = 0; col < 9; col++) {
+            // Find an empty cell
+            if (mat[row][col] == 0) {
+                // Try numbers from 1 to 9
+                for (int num = 1; num <= 9; num++) {
+                    // Check if the number is valid
+                    if (isSafe(mat, row, col, num)) {
+                        // Place the number
+                        mat[row][col] = num;
+
+                        // Recursively solve the rest of the grid
+                        if (solve(mat)) {
+                            return true;
+                        }
+
+                        // Backtrack if the solution is not feasible
+                        mat[row][col] = 0;
+                    }
+                }
+                // If no number works, return false
+                return false;
+            }
+        }
+    }
+    // If no empty cells are left, Sudoku is solved
+    return true;
+}
+
+// Main function to solve the Sudoku
+void solveSudoku(vector<vector<int>>& mat) {
+    solve(mat);
+}
+};
+
+//{ Driver Code Starts.
+
+vector<int> inputLine() {
+    string str;
+    getline(cin, str);
+    stringstream ss(str);
+    int num;
+    vector<int> res;
+    while (ss >> num) {
+        res.push_back(num);
+    }
+    return res;
+}
+
+int main() {
+    int t;
+    cin >> t;
+    cin.ignore();
+    while (t--) {
+        vector<vector<int>> grid;
+        for (int i = 0; i < 9; i++) {
+            vector<int> v = inputLine();
+            grid.push_back(v);
+        }
+
+        Solution ob;
+
+        ob.solveSudoku(grid);
+
+        for (auto v : grid) {
+            for (auto elem : v) {
+                cout << elem << " ";
+            }
+            cout << endl;
+        }
+
+        cout << "~" << endl;
+    }
+    return 0;
+}
+// } Driver Code Ends