Merge pull request #1541 from printjin-gmailcom/main

[printjin-gmailcom] Week 10 Solutions

Author: printjin-gmailcom

course-schedule/printjin-gmailcom.py

@@ -0,0 +1,23 @@
+class Solution:
+    def canFinish(self, numCourses, prerequisites):
+        from collections import defaultdict
+        graph = defaultdict(list)
+        for a, b in prerequisites:
+            graph[b].append(a)
+        visited = [0] * numCourses  
+        def dfs(course):
+            if visited[course] == 1:
+                return False  
+            if visited[course] == 2:
+                return True   
+            visited[course] = 1  
+            for next_course in graph[course]:
+                if not dfs(next_course):
+                    return False
+            visited[course] = 2  
+            return True
+        for course in range(numCourses):
+            if not dfs(course):
+                return False
+        
+        return True

invert-binary-tree/printjin-gmailcom.py

@@ -0,0 +1,8 @@
+class Solution:
+    def invertTree(self, root: Optional[TreeNode]) -> Optional[TreeNode]:
+        if not root:
+            return None
+        root.left, root.right = root.right, root.left
+        self.invertTree(root.left)
+        self.invertTree(root.right)
+        return root

jump-game/printjin-gmailcom.py

@@ -0,0 +1,8 @@
+class Solution:
+    def canJump(self, nums):
+        max_reach = 0
+        for i in range(len(nums)):
+            if i > max_reach:
+                return False
+            max_reach = max(max_reach, i + nums[i])
+        return True

merge-k-sorted-lists/printjin-gmailcom.py

@@ -0,0 +1,15 @@
+from typing import List, Optional
+class Solution:
+    def mergeKLists(self, lists)]:
+        values = []
+        for l in lists:
+            while l:
+                values.append(l.val)
+                l = l.next
+        values.sort()
+        dummy = ListNode(0)
+        current = dummy
+        for val in values:
+            current.next = ListNode(val)
+            current = current.next
+        return dummy.next

search-in-rotated-sorted-array/printjin-gmailcom.py

@@ -0,0 +1,18 @@
+class Solution:
+    def search(self, nums, target):
+        left, right = 0, len(nums) - 1
+        while left <= right:
+            mid = (left + right) // 2
+            if nums[mid] == target:
+                return mid
+            if nums[left] <= nums[mid]:
+                if nums[left] <= target < nums[mid]:
+                    right = mid - 1
+                else:
+                    left = mid + 1
+            else:
+                if nums[mid] < target <= nums[right]:
+                    left = mid + 1
+                else:
+                    right = mid - 1
+        return -1