add valid sudoku

company/apple/ValidSudoku.java

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+//Determine if a Sudoku is valid, according to: Sudoku Puzzles - The Rules. (http://sudoku.com.au/TheRules.aspx)
+//The Sudoku board could be partially filled, where empty cells are filled with the character '.'.
+//A partially filled sudoku which is valid.
+
+//Note:
+//A valid Sudoku board (partially filled) is not necessarily solvable. Only the filled cells need to be validated.
+
+class ValidSudoku {
+    public boolean isValidSudoku(char[][] board) {
+        for(int i = 0; i < board.length; i++){
+            HashSet<Character> rows = new HashSet<Character>();
+            HashSet<Character> columns = new HashSet<Character>();
+            HashSet<Character> box = new HashSet<Character>();
+            for (int j = 0; j < board[0].length; j++){
+                if(board[i][j] != '.' && !rows.add(board[i][j])) {
+                    return false;
+                }
+                if(board[j][i]!='.' && !columns.add(board[j][i])) {
+                    return false;
+                }
+                int rowIndex = (i / 3) * 3;
+                int columnIndex = (i % 3) * 3;
+                if(board[rowIndex + j / 3][columnIndex + j % 3] != '.' && !box.add(board[rowIndex + j / 3][columnIndex + j % 3])) {
+                    return false;
+                }
+            }
+        }
+        return true;
+    }
+}
+

company/snapchat/ValidSudoku.java

@@ -0,0 +1,31 @@
+//Determine if a Sudoku is valid, according to: Sudoku Puzzles - The Rules. (http://sudoku.com.au/TheRules.aspx)
+//The Sudoku board could be partially filled, where empty cells are filled with the character '.'.
+//A partially filled sudoku which is valid.
+
+//Note:
+//A valid Sudoku board (partially filled) is not necessarily solvable. Only the filled cells need to be validated.
+
+class ValidSudoku {
+    public boolean isValidSudoku(char[][] board) {
+        for(int i = 0; i < board.length; i++){
+            HashSet<Character> rows = new HashSet<Character>();
+            HashSet<Character> columns = new HashSet<Character>();
+            HashSet<Character> box = new HashSet<Character>();
+            for (int j = 0; j < board[0].length; j++){
+                if(board[i][j] != '.' && !rows.add(board[i][j])) {
+                    return false;
+                }
+                if(board[j][i]!='.' && !columns.add(board[j][i])) {
+                    return false;
+                }
+                int rowIndex = (i / 3) * 3;
+                int columnIndex = (i % 3) * 3;
+                if(board[rowIndex + j / 3][columnIndex + j % 3] != '.' && !box.add(board[rowIndex + j / 3][columnIndex + j % 3])) {
+                    return false;
+                }
+            }
+        }
+        return true;
+    }
+}
+

company/uber/ValidSudoku.java

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+//Determine if a Sudoku is valid, according to: Sudoku Puzzles - The Rules. (http://sudoku.com.au/TheRules.aspx)
+//The Sudoku board could be partially filled, where empty cells are filled with the character '.'.
+//A partially filled sudoku which is valid.
+
+//Note:
+//A valid Sudoku board (partially filled) is not necessarily solvable. Only the filled cells need to be validated.
+
+class ValidSudoku {
+    public boolean isValidSudoku(char[][] board) {
+        for(int i = 0; i < board.length; i++){
+            HashSet<Character> rows = new HashSet<Character>();
+            HashSet<Character> columns = new HashSet<Character>();
+            HashSet<Character> box = new HashSet<Character>();
+            for (int j = 0; j < board[0].length; j++){
+                if(board[i][j] != '.' && !rows.add(board[i][j])) {
+                    return false;
+                }
+                if(board[j][i]!='.' && !columns.add(board[j][i])) {
+                    return false;
+                }
+                int rowIndex = (i / 3) * 3;
+                int columnIndex = (i % 3) * 3;
+                if(board[rowIndex + j / 3][columnIndex + j % 3] != '.' && !box.add(board[rowIndex + j / 3][columnIndex + j % 3])) {
+                    return false;
+                }
+            }
+        }
+        return true;
+    }
+}

leetcode/hash-table/ValidSudoku.java

@@ -0,0 +1,31 @@
+//Determine if a Sudoku is valid, according to: Sudoku Puzzles - The Rules. (http://sudoku.com.au/TheRules.aspx)
+//The Sudoku board could be partially filled, where empty cells are filled with the character '.'.
+//A partially filled sudoku which is valid.
+
+//Note:
+//A valid Sudoku board (partially filled) is not necessarily solvable. Only the filled cells need to be validated.
+
+class ValidSudoku {
+    public boolean isValidSudoku(char[][] board) {
+        for(int i = 0; i < board.length; i++){
+            HashSet<Character> rows = new HashSet<Character>();
+            HashSet<Character> columns = new HashSet<Character>();
+            HashSet<Character> box = new HashSet<Character>();
+            for (int j = 0; j < board[0].length; j++){
+                if(board[i][j] != '.' && !rows.add(board[i][j])) {
+                    return false;
+                }
+                if(board[j][i]!='.' && !columns.add(board[j][i])) {
+                    return false;
+                }
+                int rowIndex = (i / 3) * 3;
+                int columnIndex = (i % 3) * 3;
+                if(board[rowIndex + j / 3][columnIndex + j % 3] != '.' && !box.add(board[rowIndex + j / 3][columnIndex + j % 3])) {
+                    return false;
+                }
+            }
+        }
+        return true;
+    }
+}
+