Create 0678-valid-parenthesis-string.swift

Author: drxlx

swift/0678-valid-parenthesis-string.swift

@@ -0,0 +1,29 @@
+class Solution {
+    func checkValidString(_ s: String) -> Bool {
+        var leftMin = 0
+        var leftMax = 0
+
+        for c in s {
+            if c == "(" {
+                leftMin += 1
+                leftMax += 1
+            } else if c == ")" {
+                leftMin -= 1
+                leftMax -= 1
+            } else {
+                leftMin -= 1
+                leftMax += 1
+            }
+
+            if leftMax < 0 {
+                return false
+            }
+
+            if leftMin < 0 {
+                leftMin = 0
+            }
+        }
+
+        return leftMin == 0
+    }
+}