https://leetcode.com/problems/search-insert-position/#/description

Given a sorted array and a target value, return the index if the target is found. If not, return the index where it would be if it were inserted in order.
You may assume no duplicates in the array.
Here are few examples.
[1,3,5,6], 5 → 2
[1,3,5,6], 2 → 1
[1,3,5,6], 7 → 4
[1,3,5,6], 0 → 0

# Time O(logN)
# Space O(1)
# Binary Search
class Solution(object):
    def searchInsert(self, nums, target):
        """
        :type nums: List[int]
        :type target: int
        :rtype: int
        """
        
        low = 0
        high = len(nums) - 1
        if nums[low] > target:
            return low
        if nums[high] < target:
            return high + 1
        while low <= high:
            #当low=high时，如果此时nums[mid=low=high] != target,则意味着
            #if nums[mid] > target,low = mid=high=0,high = mid - 1 will less than low
            #if nums[mid] < target,low = mid + 1 wil bigger than high
            mid = (low + high ) / 2
            if nums[mid] < target:
                low = mid + 1
                if low < len(nums):
                    if nums[low] >target:
                        return low
                else:
                    return len(nums)
            elif nums[mid] > target:
                high = mid - 1
                if high >= 0 :
                    if nums[high] < target:
                        return high + 1
                else:
                    return 0
                    
            else:
                return mid