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LC_Binary_Tree.py
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LC_Binary_Tree.py
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"""
704. Binary Search
Given an array of integers nums which is sorted in ascending order, and an integer target, write a function to search target in nums. If target exists, then return its index. Otherwise, return -1.
You must write an algorithm with O(log n) runtime complexity.
Example 1:
Input: nums = [-1,0,3,5,9,12], target = 9
Output: 4
Explanation: 9 exists in nums and its index is 4
Example 2:
Input: nums = [-1,0,3,5,9,12], target = 2
Output: -1
Explanation: 2 does not exist in nums so return -1
Constraints:
1 <= nums.length <= 104
-104 < nums[i], target < 104
All the integers in nums are unique.
nums is sorted in ascending order.
"""
class Solution(object):
def search(self, nums, target):
"""
:type nums: List[int]
:type target: int
:rtype: int
"""
def rec(nums, start, end, target):
mid = start + (end - start)/2
if start > end or end < start:
return -1
if nums[mid] == target:
return mid
if nums[mid] < target:
return rec(nums, mid+1, end, target)
if nums[mid] > target:
return rec (nums, start, mid-1, target)
return rec(nums, 0, len(nums)-1 ,target)