[printjin-gmailcom] Week 8 solutions

clone-graph/printjin-gmailcom.py

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+from collections import deque
+from typing import Optional
+
+class Solution:
+    def cloneGraph(self, node: Optional['Node']) -> Optional['Node']:
+        if not node:
+            return None
+        old_to_new = {node: Node(node.val)}
+        queue = deque([node])
+        while queue:
+            current = queue.popleft()
+            for neighbor in current.neighbors:
+                if neighbor not in old_to_new:
+                    old_to_new[neighbor] = Node(neighbor.val)
+                    queue.append(neighbor)
+                old_to_new[current].neighbors.append(old_to_new[neighbor])
+        return old_to_new[node]

longest-common-subsequence/printjin-gmailcom.py

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+class Solution:
+    def longestCommonSubsequence(self, text1, text2):
+        m, n = len(text1), len(text2)
+        dp = [[0] * (n + 1) for _ in range(m + 1)]
+        for i in range(1, m + 1):
+            for j in range(1, n + 1):
+                if text1[i - 1] == text2[j - 1]:
+                    dp[i][j] = dp[i - 1][j - 1] + 1
+                else:
+                    dp[i][j] = max(dp[i - 1][j], dp[i][j - 1])
+        return dp[m][n]

longest-repeating-character-replacement/printjin-gmailcom.py

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+class Solution:
+    def characterReplacement(self, s, k):
+        count = [0] * 26
+        left = 0
+        max_count = 0
+        res = 0
+        for right in range(len(s)):
+            count[ord(s[right]) - ord('A')] += 1
+            max_count = max(max_count, count[ord(s[right]) - ord('A')])
+            while (right - left + 1) - max_count > k:
+                count[ord(s[left]) - ord('A')] -= 1
+                left += 1
+            res = max(res, right - left + 1)
+        return res

palindromic-substrings/printjin-gmailcom.py

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+class Solution:
+    def countSubstrings(self, s):
+        count = 0
+        for center in range(len(s)):
+            left, right = center, center
+            while left >= 0 and right < len(s) and s[left] == s[right]:
+                count += 1
+                left -= 1
+                right += 1
+            left, right = center, center + 1
+            while left >= 0 and right < len(s) and s[left] == s[right]:
+                count += 1
+                left -= 1
+                right += 1
+        return count

reverse-bits/printjin-gmailcom.py

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+class Solution:
+    def reverseBits(self, n):
+        n = (n >> 16) | (n << 16)
+        n = ((n & 0xff00ff00) >> 8) | ((n & 0x00ff00ff) << 8)
+        n = ((n & 0xf0f0f0f0) >> 4) | ((n & 0x0f0f0f0f) << 4)
+        n = ((n & 0xcccccccc) >> 2) | ((n & 0x33333333) << 2)
+        n = ((n & 0xaaaaaaaa) >> 1) | ((n & 0x55555555) << 1)
+        return n