Merge pull request #21 from shimmer12/main

Added 37. Sudoku Solver.cpp

Author: kanishkaa24

37. Sudoku Solver.cpp

@@ -0,0 +1,36 @@
+class Solution {
+ public:
+  void Sudokosolr(vector<vector<char>>& board) {
+    sol(board, 0);
+  }
+
+ private:
+  bool sol(vector<vector<char>>& board, int s) {
+    if (s == 81)
+      return true;
+
+    const int i = s / 9;
+    const int j = s % 9;
+
+    if (board[i][j] != '.')
+      return sol(board, s + 1);
+
+    for (char a= '1'; a<= '9'; ++a)
+      if (isValid(board, i, j, a)) {
+        board[i][j] = a;
+        if (sol(board, s + 1))
+          return true;
+        board[i][j] = '.';
+      }
+
+    return false;
+  }
+
+  bool isValid(vector<vector<char>>& board, int row, int col, char a) {
+    for (int i = 0; i < 9; ++i)
+      if (board[i][col] == a|| board[row][i] == a||
+          board[3 * (row / 3) + i / 3][3 * (col / 3) + i % 3] == a)
+        return false;
+    return true;
+  }
+};