题解 | #二分查找-II#

寻找左边界的二分搜索。

#
# 代码中的类名、方法名、参数名已经指定，请勿修改，直接返回方法规定的值即可
#
# 如果目标值存在返回下标，否则返回 -1
# @param nums int整型一维数组 
# @param target int整型 
# @return int整型
#
class Solution:
    def search(self , nums , target ):
        # write code here
        n = len(nums)
        if n <= 0:
            return -1
        lo, hi = 0, n-1
        mid = 0
        while lo <= hi:
            mid = lo+(hi-lo)/2
            if nums[mid] < target:
                lo = mid + 1
            else:
                hi = mid - 1
        if mid >= n or mid < 0:
            return -1
        elif nums[mid] == target:
            return mid
        elif mid+1 >= n or mid+1 < 0:
            return -1
        elif nums[mid+1] == target:
            return mid + 1
        else:
            return -1