[8804who] WEEK 11 solutions

binary-tree-maximum-path-sum/8804who.py

@@ -0,0 +1,31 @@
+# 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 __init__(self):
+        self.answer = -1e9
+
+    def maxPathSum(self, root: Optional[TreeNode]) -> int:
+        self.getSum(root, 0)
+        return self.answer
+
+    def getSum(self, node, depth):
+        val = node.val
+        leftMax = self.getSum(node.left, depth+1) if node.left else 0
+        rightMax = self.getSum(node.right, depth+1) if node.right else 0
+
+        temp = val + (leftMax if leftMax > 0 else 0) + (rightMax if rightMax > 0 else 0)
+
+        if self.answer < temp:
+            self.answer = temp
+
+        if leftMax > rightMax:
+            val += leftMax if leftMax > 0 else 0
+        else:
+            val += rightMax if rightMax > 0 else 0
+
+        return val
+

merge-intervals/8804who.py

@@ -0,0 +1,15 @@
+class Solution:
+    def merge(self, intervals: List[List[int]]) -> List[List[int]]:
+        intervals.sort()
+
+        start = intervals[0][0]
+        end = intervals[0][1]
+        answer = []
+        for interval in intervals[1:]+[[10001, 0]]:
+            if end < interval[0]:
+                answer.append([start, end])
+                start = interval[0]
+            if interval[1] > end:
+                end = interval[1]
+        return answer
+

missing-number/8804who.py

@@ -0,0 +1,4 @@
+class Solution:
+    def missingNumber(self, nums: List[int]) -> int:
+        return (len(nums)*(len(nums)+1)//2)-sum(nums)
+

reorder-list/8804who.py

@@ -0,0 +1,30 @@
+from collections import deque
+# Definition for singly-linked list.
+# class ListNode:
+#     def __init__(self, val=0, next=None):
+#         self.val = val
+#         self.next = next
+class Solution:
+    def __init__(self):
+        self.q = deque()
+
+    def reorderList(self, head: Optional[ListNode]) -> None:
+        """
+        Do not return anything, modify head in-place instead.
+        """
+        temp = head
+
+        while temp:
+            self.q.append(temp.val)
+            temp = temp.next
+
+        self.makeList(head, 0)
+
+    def makeList(self, node, n):
+        if n == 0:
+            node.val = self.q.popleft()
+        else:
+            node.val = self.q.pop()
+        if self.q:
+            self.makeList(node.next, (n+1)%2)
+