Update 37. Sudoku Solver.md

TBXark · web-flow · commit afd92a5c992f · 2020-07-29T23:55:49.000+08:00
diff --git a/37. Sudoku Solver.md b/37. Sudoku Solver.md
@@ -27,6 +27,7 @@ A sudoku puzzle...
 
 # Solution
 
+扫描遍历
 ```swift
 
 class Solution {
@@ -85,3 +86,74 @@ class Solution {
 }
 
 ```
+
+
+按照权重遍历
+```swift
+
+class Solution {
+    static let num: [Character] = ["1", "2", "3", "4", "5", "6", "7", "8", "9"]
+    func solveSudoku(_ board: inout [[Character]]) {
+        var clo = [Set<Character>].init(repeating: Set<Character>(), count: 9)
+        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)]()
+        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))
+                    continue
+                }
+                clo[y].insert(c)
+                row[x].insert(c)
+                block[x/3 + (y/3) * 3].insert(c)
+            }
+        }
+        let _clo = clo.map({ $0.count })
+        let _row = row.map({ $0.count })
+        let _block = block.map({ $0.count })
+        for i in 0..<points.count {
+            let (x, y) = points[i].p
+            points[i].c = _clo[y] + _row[x] + _block[x/3 + (y/3) * 3]
+        }
+        _ = fillGrid(index: 0,
+                     point: points.sorted(by: { $0.c > $1.c }).map({ $0.p }),
+                     board: &board,
+                     clo: &clo,
+                     row: &row,
+                     block: &block)
+    }
+    
+    
+    func fillGrid(index: Int,
+                  point: [(x: Int, y: Int)],
+                  board: inout [[Character]],
+                  clo: inout [Set<Character>],
+                  row: inout [Set<Character>],
+                  block: inout [Set<Character>]) -> Bool {
+        if index == point.count  {
+            return true
+        }
+        let (x, y) = point[index]
+        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, point: point, 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
+    }
+}
+
+```
