面試常考算法——查找類算法

1.二分查找升級版

查找出第一個下標和最後一個下標

def helper(nums,target,left):
    start = 0
    end = len(nums)
    while start < end:
        mid = (start + end) // 2
        if nums[mid] > target or(left and nums[mid] == target):
            end = mid
        else:
            start = mid + 1
    return start

def searchRange(nums, target）:
    left = helper(nums,target,True)
    if left == len(nums) or nums[left] != target:
        return [-1,-1]
    return[left, helper(nums,target,False)-1]