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Author: jlyang1990

167. Two Sum II - Input array is sorted.py

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+class Solution(object):
+    def twoSum(self, numbers, target):
+        """
+        :type numbers: List[int]
+        :type target: int
+        :rtype: List[int]
+        """
+        # if numbers[i]+numbers[j]>target, then numbers[k]+numbers[j]>target, k=i+1,...,j-1, thus exclude them
+        # the next step is to investigate numbers[i]+numbers[j-1]
+        left = 0
+        right = len(numbers)-1
+        while left < right:
+            if numbers[left] + numbers[right] == target:
+                return [left+1, right+1]
+            elif numbers[left] + numbers[right] > target:
+                right -= 1
+            else:
+                left += 1

236. Lowest Common Ancestor of a Binary Tree.py

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+# Definition for a binary tree node.
+# class TreeNode(object):
+#     def __init__(self, x):
+#         self.val = x
+#         self.left = None
+#         self.right = None
+
+class Solution(object):
+    def lowestCommonAncestor(self, root, p, q):
+        """
+        :type root: TreeNode
+        :type p: TreeNode
+        :type q: TreeNode
+        :rtype: TreeNode
+        """
+        if root in (None, p, q):
+            return root
+        left = self.lowestCommonAncestor(root.left, p, q)
+        right = self.lowestCommonAncestor(root.right, p, q)
+        if left and right:
+            return root
+        return left or right