[Neetcode] Valid sudoku

Author: GauthamBanasandra

Neetcode/CMakeLists.txt

@@ -6,3 +6,4 @@ set(CMAKE_CXX_STANDARD 17)
 add_executable(Two_sum_neetcode "Two sum/Two sum.cpp")
 add_executable(Group_anagrams_neetcode "Group anagrams/Group anagrams.cpp")
 add_executable(Top_K_Frequent_Elements "Top K Frequent Elements/Top K Frequent Elements.cpp")
+add_executable(Valid_sudoku_neetcode "Valid sudoku/Valid sudoku.cpp")

Neetcode/Valid sudoku/Valid sudoku.cpp

@@ -0,0 +1,73 @@
+#include <bitset>
+#include <iostream>
+#include <vector>
+
+class Solution {
+public:
+  bool isValidSudoku(std::vector<std::vector<char>> &board);
+
+private:
+  static bool validateElement(std::bitset<9> &validity, char element);
+};
+
+bool Solution::isValidSudoku(std::vector<std::vector<char>> &board) {
+  std::bitset<9> row_validity, col_validity, box_validity;
+
+  for (std::size_t i = 0; i < board.size(); ++i) {
+    row_validity.reset();
+    col_validity.reset();
+    for (std::size_t j = 0; j < board[i].size(); ++j) {
+      if (!validateElement(row_validity, board[i][j])) {
+        return false;
+      }
+      if (!validateElement(col_validity, board[j][i])) {
+        return false;
+      }
+    }
+  }
+
+  for (std::size_t i_box_row = 0; i_box_row < board.size(); i_box_row += 3) {
+    for (std::size_t j_box_row = 0; j_box_row < board.size(); j_box_row += 3) {
+      box_validity.reset();
+      for (std::size_t i = i_box_row; i < i_box_row + 3; ++i) {
+        for (std::size_t j = j_box_row; j < j_box_row + 3; ++j) {
+          if (!validateElement(box_validity, board[i][j])) {
+            return false;
+          }
+        }
+      }
+    }
+  }
+
+  return true;
+}
+
+bool Solution::validateElement(std::bitset<9> &validity, const char element) {
+  if (element == '.') {
+    return true;
+  }
+
+  const auto num = element - '1';
+  if (validity.test(num)) {
+    return false;
+  }
+
+  validity.set(num);
+  return true;
+}
+
+int main(int argc, char *argv[]) {
+  std::vector<std::vector<char>> board{
+      {'1', '2', '.', '.', '3', '.', '.', '.', '.'},
+      {'4', '.', '.', '5', '.', '.', '.', '.', '.'},
+      {'.', '9', '1', '.', '.', '.', '.', '.', '3'},
+      {'5', '.', '.', '.', '6', '.', '.', '.', '4'},
+      {'.', '.', '.', '8', '.', '3', '.', '.', '5'},
+      {'7', '.', '.', '.', '2', '.', '.', '.', '6'},
+      {'.', '.', '.', '.', '.', '.', '2', '.', '.'},
+      {'.', '.', '.', '4', '1', '9', '.', '.', '8'},
+      {'.', '.', '.', '.', '8', '.', '.', '7', '9'}};
+
+  std::cout << Solution().isValidSudoku(board) << std::endl;
+  return 0;
+}