leetcode35 Search Insert Position

"""
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.
Example 1:
Input: [1,3,5,6], 5
Output: 2
Example 2:
Input: [1,3,5,6], 2
Output: 1
Example 3:
Input: [1,3,5,6], 7
Output: 4
Example 4:
Input: [1,3,5,6], 0
Output: 0
"""
"""
本题提供两种解法，第一种是遍历有序的数组
遇到大于等于 target的位置插入
"""
class Solution1:
    def searchInsert(self, nums, target):
        if nums[-1] < target:  #边界条件
            return len(nums)
        if nums[0] > target:
            return 0
        for i in range(len(nums)):
            if nums[i] >= target: #！！！关键点
                return i

"""
二分法
对于二分法的 left right mid之间的转换 
目前的思路是 更换测试用例 来不断修正如何转换
传送门：https://www.jianshu.com/p/46b8d8a55888
"""
class Solution2:
    def searchInsert(self, nums, target):
        if not nums:
            return 0
        left = 0
        right = len(nums)
        while left < right:
            mid = (left+right)//2
            if nums[mid] >= target:
                right = mid
            else:
                left = mid + 1
        return left