2021-01-20 Python百日打卡学习自【夸可编程】

'''

第20天：二分查找最右

每日一题 夸克编程 昨天
题目

输入一个升序的整数数组，和一个整数，使用二分查找在数组中搜索该整数，返回最靠右的位置。
如果不存在返回-1
例子

binarySearchRightmost([1,2,3,3,3,4],3) -> 4
binarySearchRightmost([10,14,20,21,22,22],22) -> 5
binarySearchRightmost([5,10,12],3) -> -1
假设

输入的数组不为空
输入的数组为升序
'
'''

def binarySearch(nums, left, right, target):
    if left <= right:
        mid = (left + right)//2
        if nums[mid] == target:
            return mid
        elif nums[mid] < target:
            binarySearch(nums, mid+1, right, target)
        else:
            binarySearch(nums, left, mid-1, target)
    return 0

def binarySearchRightmost(nums, target):
    index = -1
    if target < nums[0] or target > nums[-1]:
        return -1
    if target == nums[-1]:
        return len(nums)-1
    index = binarySearch(nums, 0, len(nums)-1, target)

    while index+1 < len(nums)-1 and nums[index] == nums[index+1]:
        index += 1

    return index


print(binarySearchRightmost([1,2,3,3,3,4],3))# -> 4
print(binarySearchRightmost([1,2,3,3,3,4],1))# -> 4
print(binarySearchRightmost([10,14,20,21,22,22],22))# -> 5
print(binarySearchRightmost([5,10,12],3))# -> -1
print(binarySearchRightmost([5],7))# -> -1



网站答案

解法1
def binarySearchRightmost(nums,target):
    rightmost_idx = -1
    left , right = 0 , len(nums) - 1
    while left <= right:
        mid = (left + right) // 2
        if nums[mid] == target:
            rightmost_idx = mid
            left = mid + 1
        elif nums[mid] < target:
            left = mid + 1
        elif nums[mid] > target:
            right = mid - 1 
    return rightmost_idx
性能：
时间复杂度O(logn)
空间复杂度O(1)