add isValidSudoku.cpp

Author: kamyu104

C++/isValidSudoku.cpp

@@ -0,0 +1,47 @@
+// Time Complexity: O(n^2)
+// Space Complexity: O(n)
+
+class Solution {
+    public:
+        bool isValidSudoku(vector<vector<char> > &board) {
+            bool used[9];
+
+            for(int i = 0; i < 9; ++i) {
+                fill(used, used + 9, false);
+                for(int j = 0; j < 9; ++j) {
+                    if(!check(board[i][j], used))
+                        return false;
+                }
+
+                fill(used, used + 9, false);
+                for(int j = 0; j < 9; ++j) {
+                    if(!check(board[j][i], used))
+                        return false;
+                }
+            }
+
+            for(int r = 0; r < 3; ++r) {
+                for(int c = 0; c < 3; ++c) {
+                    fill(used, used + 9, false);
+                    for(int i = 3 * r;  i < 3 * (r + 1); ++i) {
+                        for(int j = 3 * c;  j < 3 * (c + 1); ++j) {
+                            if(!check(board[i][j], used))
+                                return false;
+                        }
+                    }
+                }
+            }
+
+            return true;
+        }
+
+    private:
+        bool check(char c, bool used[9]) {
+            if(c != '.') {
+                if(used[c - '1'])
+                    return false;
+                used[c - '1'] = true;
+            }
+            return true;
+        }
+};