3

Author: kedebug

SudokuSolver/SudokuSolver.cpp

@@ -0,0 +1,54 @@
+class Solution {
+public:
+    bool visited_cells[20][20];
+    bool visited_row[20][20];
+    bool visited_col[20][20];
+    
+    void solveSudoku(vector<vector<char>>& board) {
+        // Start typing your C/C++ solution below
+        // DO NOT write int main() function
+        
+        memset(visited_cells, false, sizeof(visited_cells));  
+        memset(visited_row, false, sizeof(visited_row));    
+        memset(visited_col, false, sizeof(visited_col));  
+        
+        for (int i = 0; i < 9; i++) {
+            for (int j = 0; j < 9; j++) {
+                if (board[i][j] != '.') {
+                    int cell = (i / 3) * 3 + j / 3;
+                    int x = board[i][j] - '0';
+                    visited_cells[cell][x] = true;
+                    visited_row[i][x] = visited_col[j][x] = true;
+                }
+            }
+        }
+        
+        isValidSudokuHelper(board, 0);
+    }
+    
+    bool isValidSudokuHelper(vector<vector<char>>& board, int step) {
+        if (step == 81) return true;
+        
+        int row = step / 9;
+        int col = step % 9;
+        int cell = (row / 3) * 3 + col / 3;
+        
+        if (board[row][col] != '.') {
+            return isValidSudokuHelper(board, step + 1);
+        }
+        for (int i = 1; i <= 9; i++) {
+            if (!visited_cells[cell][i] && !visited_row[row][i] && !visited_col[col][i]) {
+                visited_cells[cell][i] = true;
+                visited_row[row][i] = visited_col[col][i] = true;
+                board[row][col] = '0' + i;
+                bool flag = isValidSudokuHelper(board, step + 1);
+                if (flag) return true;
+                board[row][col] = '.';
+                visited_cells[cell][i] = false;
+                visited_row[row][i] = visited_col[col][i] = false;
+            }
+        }
+        return false;
+    }
+};
+