insert-interval/ppxyn1.py

-Original file line number
+Diff line change
@@ -0,0 +1,32 @@
+    # idea: -
+    # Time Complexity: O(n)
+    class Solution:
+        def insert(self, intervals: List[List[int]], newInterval: List[int]) -> List[List[int]]:
+            res = []
+            # Ex,. newInterval = [2,5]
+            for i in range(len(intervals)):
+                start, end = intervals[i]
+                # [2,5] > [1,5]
+                # already passed
+                if end < newInterval[0]:
+                    res.append(intervals[i])
+                # not started yet
+                # (2)
+                elif newInterval[1] < start:
+                    res.append(newInterval) # [1,5]
+                    for j in range(i, len(intervals)):
+                        res.append(intervals[j])
+                    return res
+                else:
+                    # (1)
+                    # overlapping
+                    newInterval[0] = min(newInterval[0], start)
+                    newInterval[1] = max(newInterval[1], end)
+            res.append(newInterval)
+            return res

kth-smallest-element-in-a-bst/ppxyn1.py

-Original file line number
+Diff line change
@@ -0,0 +1,30 @@
+    # 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
+    #idea : DFS (inorder)
+    #Time Complexity: O(n)
+    class Solution:
+        def kthSmallest(self, root: Optional[TreeNode], k: int) -> int:
+            stack = []
+            cnt = 0
+            curr = root
+            if not curr:
+                return
+            while curr or stack:
+                while curr:
+                    stack.append(curr)
+                    curr = curr.left
+                curr = stack.pop()
+                cnt += 1
+                if cnt == k:
+                    return curr.val
+                curr = curr.right

lowest-common-ancestor-of-a-binary-search-tree/ppxyn1.py

-Original file line number
+Diff line change
@@ -0,0 +1,23 @@
+    # Definition for a binary tree node.
+    # class TreeNode:
+    #     def __init__(self, x):
+    #         self.val = x
+    #         self.left = None
+    #         self.right = None
+    # idea: BST property
+    # Time Complexity : O(long n)
+    class Solution:
+        def lowestCommonAncestor(self, root: 'TreeNode', p: 'TreeNode', q: 'TreeNode') -> 'TreeNode':
+            cur = root
+            while cur:
+                if p.val > cur.val and q.val > cur.val:
+                    cur = cur.right
+                elif p.val < cur.val and q.val < cur.val:
+                    cur = cur.left
+                else:
+                    return cur

[ppxyn1] WEEK 13 solutions #2311

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ppxyn1 wants to merge 4 commits into DaleStudy:main from ppxyn1:main

+85 −0

-Original file line number
+Diff line change
@@ -0,0 +1,32 @@
+    # idea: -
+    # Time Complexity: O(n)
+    class Solution:
+        def insert(self, intervals: List[List[int]], newInterval: List[int]) -> List[List[int]]:
+            res = []
+            # Ex,. newInterval = [2,5]
+            for i in range(len(intervals)):
+                start, end = intervals[i]
+                # [2,5] > [1,5]
+                # already passed
+                if end < newInterval[0]:
+                    res.append(intervals[i])
+                # not started yet
+                # (2)
+                elif newInterval[1] < start:
+                    res.append(newInterval) # [1,5]
+                    for j in range(i, len(intervals)):
+                        res.append(intervals[j])
+                    return res
+                else:
+                    # (1)
+                    # overlapping
+                    newInterval[0] = min(newInterval[0], start)
+                    newInterval[1] = max(newInterval[1], end)
+            res.append(newInterval)
+            return res

-Original file line number
+Diff line change
@@ -0,0 +1,30 @@
+    # 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
+    #idea : DFS (inorder)
+    #Time Complexity: O(n)
+    class Solution:
+        def kthSmallest(self, root: Optional[TreeNode], k: int) -> int:
+            stack = []
+            cnt = 0
+            curr = root
+            if not curr:
+                return
+            while curr or stack:
+                while curr:
+                    stack.append(curr)
+                    curr = curr.left
+                curr = stack.pop()
+                cnt += 1
+                if cnt == k:
+                    return curr.val
+                curr = curr.right

-Original file line number
+Diff line change
@@ -0,0 +1,23 @@
+    # Definition for a binary tree node.
+    # class TreeNode:
+    #     def __init__(self, x):
+    #         self.val = x
+    #         self.left = None
+    #         self.right = None
+    # idea: BST property
+    # Time Complexity : O(long n)
+    class Solution:
+        def lowestCommonAncestor(self, root: 'TreeNode', p: 'TreeNode', q: 'TreeNode') -> 'TreeNode':
+            cur = root
+            while cur:
+                if p.val > cur.val and q.val > cur.val:
+                    cur = cur.right
+                elif p.val < cur.val and q.val < cur.val:
+                    cur = cur.left
+                else:
+                    return cur

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