Update 37. Sudoku Solver.md

TBXark · web-flow · commit a35aef572d24 · 2020-07-30T10:06:00.000+08:00
diff --git a/37. Sudoku Solver.md b/37. Sudoku Solver.md
@@ -197,7 +197,7 @@ Runtime: 36 ms, faster than 100.00% of Swift online submissions for Sudoku Solve
 Memory Usage: 22.5 MB, less than 50.00% of Swift online submissions for Sudoku Solver.
 ```
 
-```
+```swift
 class Solution {
 
     static let num: Set<Character> = ["1", "2", "3", "4", "5", "6", "7", "8", "9"]
