update

Author: wuduhren

problems/python3/minimum-window-substring.py

@@ -0,0 +1,25 @@
+class Solution:
+    def minWindow(self, s: str, t: str) -> str:
+        if len(t)>len(s): return ""
+        
+        ans = ""
+        counter1 = collections.Counter(t)
+        charSet = set(t)
+        counter2 = collections.Counter() #sliding window in string s, index between l and r
+        charSet2 = set(s)
+        matchCount = 0 #count of char in the sliding window that counts are larger than the char count in t.
+        
+        l = 0
+        for r in range(len(s)):
+            counter2[s[r]] += 1
+            
+            if s[r] in charSet and counter1[s[r]]==counter2[s[r]]: matchCount += 1
+                
+            while l<len(s) and (s[l] not in charSet or counter2[s[l]]>counter1[s[l]]):
+                counter2[s[l]] -= 1
+                l += 1
+                
+            if matchCount==len(charSet) and (ans=="" or r-l+1<len(ans)):
+                ans = s[l:r+1]
+                
+        return ans

problems/python3/sliding-window-maximum.py

@@ -0,0 +1,18 @@
+class Solution:
+    def maxSlidingWindow(self, nums: List[int], k: int) -> List[int]:
+        ans = []
+        q = collections.deque()
+        l = r = 0
+        
+        while r<len(nums):
+            while q and nums[q[-1]]<nums[r]: q.pop()
+            q.append(r)
+            
+            while q and q[0]<l: q.popleft()
+            
+            while r-l+1==k:
+                ans.append(nums[q[0]])
+                l += 1
+            
+            r += 1
+        return ans

problems/python3/valid-parentheses.py

@@ -0,0 +1,17 @@
+class Solution:
+    def isValid(self, s: str) -> bool:
+        mapping = {')': '(', ']': '[', '}':'{'}
+        stack = []
+        
+        for c in s:
+            if c not in mapping:
+                #open parentheses
+                stack.append(c)
+            else:
+                #close parentheses
+                if stack and stack[-1]==mapping[c]:
+                    stack.pop()
+                else:
+                    return False
+        
+        return not stack