Update 37. Sudoku Solver.md

Author: TBXark

37. Sudoku Solver.md

@@ -51,37 +51,43 @@ class Solution {
     }
 
 
-    func fillGrid(index: Int,
+        func fillGrid(index: Int,
                   board: inout [[Character]],
                   clo: inout [Set<Character>],
                   row: inout [Set<Character>],
                   block: inout [Set<Character>]) -> Bool {
         guard index < 81 else {
             return true
         }
-        let x = index % 9
-        let y = index / 9
-        if board[y][x] == "." {
-            for c in Solution.num {
-                if !clo[y].contains(c), !row[x].contains(c), !block[x/3 + (y/3) * 3].contains(c) {
-                    board[y][x] = c
-                    clo[y].insert(c)
-                    row[x].insert(c)
-                    block[x/3 + (y/3) * 3].insert(c)
-                    if fillGrid(index: index + 1, board: &board, clo: &clo, row: &row, block: &block) {
-                        return true
-                    } else {
-                        clo[y].remove(c)
-                        row[x].remove(c)
-                        block[x/3 + (y/3) * 3].remove(c)
-                        board[y][x] = "."
-                    }
+        var i = index
+        var x = i % 9
+        var y = i / 9
+        while board[y][x] != "." {
+            i += 1
+            guard i < 81  else {
+               return true
+            }
+            x = i % 9
+            y = i / 9
+        }
+        
+        for c in Solution.num {
+            if !clo[y].contains(c), !row[x].contains(c), !block[x/3 + (y/3) * 3].contains(c) {
+                board[y][x] = c
+                clo[y].insert(c)
+                row[x].insert(c)
+                block[x/3 + (y/3) * 3].insert(c)
+                if fillGrid(index: i + 1, board: &board, clo: &clo, row: &row, block: &block) {
+                    return true
+                } else {
+                    clo[y].remove(c)
+                    row[x].remove(c)
+                    block[x/3 + (y/3) * 3].remove(c)
+                    board[y][x] = "."
                 }
             }
-            return false
-        } else {
-            return fillGrid(index: index + 1, board: &board, clo: &clo, row: &row, block: &block)
         }
+        return false
     }
 }
 
@@ -98,8 +104,8 @@ class Solution {
         var row = [Set<Character>].init(repeating: Set<Character>(), count: 9)
         var block = [Set<Character>].init(repeating: Set<Character>(), count: 9)
         var points = [(p: (x: Int, y: Int), c: Int)]()
+        var points = [(p: (x: Int, y: Int), c: Int)]()
         for y in 0..<9 {
-            for x in 0..<9 {
                 let c = board[y][x]
                 guard c != "." else {
                     points.append((p: (x: x, y: y), c: 0))
@@ -157,3 +163,20 @@ class Solution {
 }
 
 ```
+
+```
+对于测试数组 
+[["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"]]
+
+扫描遍历尝试填充4208次，按权重遍历调用fillGrid 340次
+
+```
+