From d5e6259f5b809a2ee28519ad78e9ac203bfd9d27 Mon Sep 17 00:00:00 2001
From: Deven <63876261+devenperez@users.noreply.github.com>
Date: Sat, 29 Nov 2025 20:33:08 -0500
Subject: [PATCH] Time: 0 ms (100%), Space: 17.6 MB (82.62%) - LeetHub

---
 .../0678-valid-parenthesis-string.py          | 61 +++++++++++++++++++
 1 file changed, 61 insertions(+)
 create mode 100644 0678-valid-parenthesis-string/0678-valid-parenthesis-string.py

diff --git a/0678-valid-parenthesis-string/0678-valid-parenthesis-string.py b/0678-valid-parenthesis-string/0678-valid-parenthesis-string.py
new file mode 100644
index 0000000..69d3703
--- /dev/null
+++ b/0678-valid-parenthesis-string/0678-valid-parenthesis-string.py
@@ -0,0 +1,61 @@
+class Solution:
+    def checkValidString(self, s: str) -> bool:
+        """
+        Complexities:
+        Time:  O(n)
+        Space: O(n)
+
+        where n = len(s)
+        """
+
+        bracketCount = 0
+        starCount = 0
+        starIndecies = []
+        usedStars = 0
+
+        # Forward pass - allocate as many *s to be (
+        # - when allocating a star, always use the star that appears first
+        for i, l in enumerate(s):
+            if l == '(':
+                bracketCount += 1
+            elif l == '*':
+                starCount += 1
+                starIndecies.append(i)
+            elif bracketCount > 0:
+                bracketCount -= 1
+            elif starCount > 0:
+                starCount -= 1
+                usedStars += 1
+            else:
+                return False
+
+        # There are already matching opening/closing brackets
+        # - all stars are assigned empty string
+        if bracketCount == 0:
+            return True
+
+        # There are more closed brackets needed than the amount of remaining stars
+        if bracketCount > 0 and bracketCount > starCount:
+            return False
+
+        # Backward pass - allocate as many *s to be )
+        # - the first `usedStars` stars are considered used from the forward pass
+        firstViableStar = starIndecies[usedStars]
+        bracketCount = 0
+        starCount = 0
+        for i in range(len(s) - 1, 0, -1):
+            l = s[i]
+
+            if l == ')':
+                bracketCount += 1
+            elif l == '*':
+                starCount += 1 if i >= firstViableStar else 0
+            elif bracketCount > 0:
+                bracketCount -= 1
+            elif starCount > 0:
+                starIndecies.pop(0)
+                starCount -= 1
+            else:
+                return False
+
+        return True
\ No newline at end of file