Update 37. Sudoku Solver.md

TBXark · web-flow · commit 7da23f950f3e · 2020-07-29T22:08:40.000+08:00
diff --git a/37. Sudoku Solver.md b/37. Sudoku Solver.md
@@ -38,6 +38,9 @@ class Solution {
         for y in 0..<9 {
             for x in 0..<9 {
                 let c = board[y][x]
+                guard c != "." else {
+                    continue
+                }
                 clo[y].insert(c)
                 row[x].insert(c)
                 block[x/3 + (y/3) * 3].insert(c)
