36. Valid Sudoku

coderbean · coderbean · commit 11e3a28b280d · 2019-03-21T17:16:58.000+08:00
diff --git a/src/leetcode/_36_/Main.java b/src/leetcode/_36_/Main.java
@@ -0,0 +1,22 @@
+package leetcode._36_;
+
+/**
+ * Created by zhangbo54 on 2019-03-04.
+ */
+public class Main {
+    public static void main(String[] args) {
+        Solution solution = new Solution();
+        char charArray[][] = {
+                {'5', '3', '.', '.', '7', '.', '.', '.', '.'},
+                {'6', '.', '.', '1', '9', '5', '.', '.', '.'},
+                {'.', '9', '8', '.', '.', '.', '.', '6', '.'},
+                {'8', '.', '.', '.', '6', '.', '.', '.', '3'},
+                {'4', '.', '.', '8', '.', '3', '.', '.', '1'},
+                {'7', '.', '.', '.', '2', '.', '.', '.', '6'},
+                {'.', '6', '.', '.', '.', '.', '2', '8', '.'},
+                {'.', '.', '.', '4', '1', '9', '.', '.', '5'},
+                {'.', '.', '.', '.', '8', '.', '.', '7', '9'}};
+        System.out.println(solution.isValidSudoku(charArray));
+    }
+}
+
diff --git a/src/leetcode/_36_/Solution.java b/src/leetcode/_36_/Solution.java
@@ -0,0 +1,60 @@
+package leetcode._36_;
+
+import java.util.ArrayList;
+import java.util.HashSet;
+import java.util.List;
+import java.util.Set;
+
+class Solution {
+    public boolean isValidSudoku(char[][] board) {
+        List<Set<Character>> hList = new ArrayList<>(27);
+        List<Set<Character>> vList = new ArrayList<>(27);
+        for (int i = 0; i < 27; i++) {
+            hList.add(new HashSet<>());
+            vList.add(new HashSet<>());
+        }
+        for (int i = 0; i < board.length; i++) {
+            for (int j = 0; j < board[i].length; j++) {
+                int vIndex = i + j / 3 * 9;
+                int hIndex = j + i / 3 * 9;
+                if (board[i][j] != '.') {
+                    if (hList.get(hIndex).contains(board[i][j]) || vList.get(vIndex).contains(board[i][j])) {
+                        return false;
+                    }
+                    hList.get(hIndex).add(board[i][j]);
+                    vList.get(vIndex).add(board[i][j]);
+                }
+            }
+        }
+        for (int i = 0; i < 9; i++) {
+            // every row
+            Set<Character> set = new HashSet<>();
+            set.addAll(vList.get(i));
+            set.addAll(vList.get(i + 9));
+            set.addAll(vList.get(i + 9 * 2));
+            if (set.size() != (vList.get(i).size() + vList.get(i + 9).size() + vList.get(i + 9 * 2).size())) {
+                return false;
+            }
+
+            // every columns
+            Set<Character> set2 = new HashSet<>();
+            set2.addAll(hList.get(i));
+            set2.addAll(hList.get(i + 9));
+            set2.addAll(hList.get(i + 9 * 2));
+            if (set2.size() != (hList.get(i).size() + hList.get(i + 9).size() + hList.get(i + 9 * 2).size())) {
+                return false;
+            }
+
+            // every little 9 grips
+            Set<Character> set3 = new HashSet<>();
+            set3.addAll(vList.get(i * 3));
+            set3.addAll(vList.get(i * 3 + 1));
+            set3.addAll(vList.get(i * 3 + 2));
+            if (set3.size() != (vList.get(i * 3).size() + vList.get(i * 3 + 1).size() + vList.get(i * 3 + 2).size())) {
+                return false;
+            }
+
+        }
+        return true;
+    }
+}
diff --git a/src/leetcode/_36_/solution.md b/src/leetcode/_36_/solution.md
@@ -0,0 +1,103 @@
+### [36\. Valid SudokuCopy for Markdown](https://leetcode.com/problems/valid-sudoku/)
+
+Difficulty: **Medium**
+
+
+Determine if a 9x9 Sudoku board is valid. Only the filled cells need to be validated **according to the following rules**:
+
+1.  Each row must contain the digits `1-9` without repetition.
+2.  Each column must contain the digits `1-9` without repetition.
+3.  Each of the 9 `3x3` sub-boxes of the grid must contain the digits `1-9` without repetition.
+
+![](https://upload.wikimedia.org/wikipedia/commons/thumb/f/ff/Sudoku-by-L2G-20050714.svg/250px-Sudoku-by-L2G-20050714.svg.png)  
+<small style="display: inline;">A partially filled sudoku which is valid.</small>
+
+The Sudoku board could be partially filled, where empty cells are filled with the character `'.'`.
+
+**Example 1:**
+
+```
+Input:
+[
+  ["5","3",".",".","7",".",".",".","."],
+  ["6",".",".","1","9","5",".",".","."],
+  [".","9","8",".",".",".",".","6","."],
+  ["8",".",".",".","6",".",".",".","3"],
+  ["4",".",".","8",".","3",".",".","1"],
+  ["7",".",".",".","2",".",".",".","6"],
+  [".","6",".",".",".",".","2","8","."],
+  [".",".",".","4","1","9",".",".","5"],
+  [".",".",".",".","8",".",".","7","9"]
+]
+Output: true
+```
+
+**Example 2:**
+
+```
+Input:
+[
+  ["8","3",".",".","7",".",".",".","."],
+  ["6",".",".","1","9","5",".",".","."],
+  [".","9","8",".",".",".",".","6","."],
+  ["8",".",".",".","6",".",".",".","3"],
+  ["4",".",".","8",".","3",".",".","1"],
+  ["7",".",".",".","2",".",".",".","6"],
+  [".","6",".",".",".",".","2","8","."],
+  [".",".",".","4","1","9",".",".","5"],
+  [".",".",".",".","8",".",".","7","9"]
+]
+Output: false
+Explanation: Same as Example 1, except with the 5 in the top left corner being 
+    modified to 8\. Since there are two 8's in the top left 3x3 sub-box, it is invalid.
+```
+
+**Note:**
+
+*   A Sudoku board (partially filled) could be valid but is not necessarily solvable.
+*   Only the filled cells need to be validated according to the mentioned rules.
+*   The given board contain only digits `1-9` and the character `'.'`.
+*   The given board size is always `9x9`.
+
+
+#### Solution
+
+Language: **Java**
+
+```java
+        }
+        for (int i = 0; i < 9; i++) {
+            // every row
+            Set<Character> set = new HashSet<>();
+            set.addAll(vList.get(i));
+            set.addAll(vList.get(i + 9));
+            set.addAll(vList.get(i + 9 * 2));
+            if (set.size() != (vList.get(i).size() + vList.get(i + 9).size() + vList.get(i + 9 * 2).size())) {
+                return false;
+            }
+​
+            // every columns
+            Set<Character> set2 = new HashSet<>();
+            set2.addAll(hList.get(i));
+            set2.addAll(hList.get(i + 9));
+            set2.addAll(hList.get(i + 9 * 2));
+            if (set2.size() != (hList.get(i).size() + hList.get(i + 9).size() + hList.get(i + 9 * 2).size())) {
+                return false;
+            }
+​
+            // every little 9 grips
+            Set<Character> set3 = new HashSet<>();
+            set3.addAll(vList.get(i * 3));
+            set3.addAll(vList.get(i * 3 + 1));
+            set3.addAll(vList.get(i * 3 + 2));
+            if (set3.size() != (vList.get(i * 3).size() + vList.get(i * 3 + 1).size() + vList.get(i * 3 + 2).size())) {
+                return false;
+            }
+​
+        }
+        return true;
+    }
+}
+​
+```
+![](https://ws3.sinaimg.cn/large/006tKfTcgy1g1ajb5r7onj30xk0u0gql.jpg)
