[8804who] WEEK 15 solutions

construct-binary-tree-from-preorder-and-inorder-traversal/8804who.py

@@ -0,0 +1,22 @@
+# Definition for a binary tree node.
+# class TreeNode:
+#     def __init__(self, val=0, left=None, right=None):
+#         self.val = val
+#         self.left = left
+#         self.right = right
+class Solution:
+    def buildTree(self, preorder: List[int], inorder: List[int]) -> Optional[TreeNode]:
+        inorder_idx = {val:idx for idx, val in enumerate(inorder) }
+        preorder_iter = iter(preorder)
+
+        def dfs(start, end):
+            if start > end:
+                return None
+
+            val = next(preorder_iter)
+            mid = inorder_idx[val]
+
+            return TreeNode(val, dfs(start, mid-1), dfs(mid+1, end))
+
+        return dfs(0, len(preorder)-1)
+

longest-palindromic-substring/8804who.py

@@ -0,0 +1,28 @@
+class Solution:
+    def longestPalindrome(self, s: str) -> str:
+        answer = ""
+        for i in range(len(s)):
+            dist = 0
+            temp = ""
+            while i-dist >= 0 and i+dist < len(s):
+                if s[i-dist] == s[i+dist]:
+                    temp = s[i-dist:i+dist+1]
+                    dist+=1
+                else:
+                    break
+            if len(temp) > len(answer):
+                answer = temp
+            if i+1 < len(s):
+                if s[i] != s[i+1]:
+                    continue
+                dist = 0
+                while i-dist >= 0 and i+1+dist < len(s):
+                    if s[i-dist] == s[i+1+dist]:
+                        temp = s[i-dist:i+dist+2]
+                        dist+=1
+                    else:
+                        break
+            if len(temp) > len(answer):
+                answer = temp
+        return answer
+

rotate-image/8804who.py

@@ -0,0 +1,37 @@
+from collections import deque
+
+class Solution:
+    def rotate(self, matrix: List[List[int]]) -> None:
+        """
+        Do not return anything, modify matrix in-place instead.
+        """
+
+        def sub(s, e):
+            q = deque()
+
+            for i in range(s, e+1):
+                q.append(matrix[s][i])
+            for i in range(s+1, e+1):
+                q.append(matrix[i][e])
+            for i in range(e-1, s-1, -1):
+                q.append(matrix[e][i])
+            for i in range(e-1, s, -1):
+                q.append(matrix[i][s])
+
+            for _ in range(e-s):
+                q.appendleft(q.pop())
+
+            for i in range(s, e+1):
+                matrix[s][i] = q.popleft()
+            for i in range(s+1, e+1):
+                matrix[i][e] = q.popleft()
+            for i in range(e-1, s-1, -1):
+                matrix[e][i] = q.popleft()
+            for i in range(e-1, s, -1):
+                matrix[i][s] = q.popleft()
+
+            if s+1 <= e-1:
+                sub(s+1, e-1)
+
+        sub(0, len(matrix)-1)
+

subtree-of-another-tree/8804who.py

@@ -0,0 +1,17 @@
+# Definition for a binary tree node.
+# class TreeNode:
+#     def __init__(self, val=0, left=None, right=None):
+#         self.val = val
+#         self.left = left
+#         self.right = right
+class Solution:
+    def isSubtree(self, root: Optional[TreeNode], subRoot: Optional[TreeNode]) -> bool:
+        def getTreeNodes(node):
+            if not node:
+                return "#"
+
+            return ":"+str(node.val)+":"+getTreeNodes(node.left)+getTreeNodes(node.right)
+
+
+        return getTreeNodes(subRoot) in getTreeNodes(root)
+