Leetcode题库——34.在排序数组中国查找元素的第一个和最后一个位置

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@author: ZZQ

@software: PyCharm

@file: searchRange.py

@time: 2018/11/12 19:19

要求：给定一个按照升序排列的整数数组 nums，和一个目标值 target。找出给定目标值在数组中的开始位置和结束位置。

你的算法时间复杂度必须是 O(log n) 级别。

如果数组中不存在目标值，返回 [-1, -1]。

示例 1:

输入: nums = [5,7,7,8,8,10], target = 8

输出: [3,4]

示例 2:

输入: nums = [5,7,7,8,8,10], target = 6

输出: [-1,-1]

思路：1. 二分查找，先找到该元素的位置，然后向前向后搜索其起止位置（好像会到O(n)）

2. 分两次搜索，二分查找，先找到起始位置，再找到停止位置。

class Solution():
    def __init__(self):
        pass

    def searchRange(self, nums, target):
        """
        :type nums: List[int]
        :type target: int
        :rtype: List[int]
        """
        nums_len = len(nums)
        start_index = -1
        end_index = -1
        if nums_len == 0:
            return [start_index, end_index]
        elif nums_len == 1:
            if nums[0] == target:
                return [0, 0]
            else:
                return [start_index, end_index]
        else:
            left = 0
            right = nums_len-1
            while left <= right:
                middle = (left + right) / 2
                if nums[middle] == target:
                    start_index = middle
                    while nums[middle] == target:
                        middle += 1
                        if middle == nums_len:
                            end_index = middle - 1
                            break
                    if end_index == -1:
                        end_index = middle - 1
                    while nums[start_index-1] == target:
                        start_index -= 1
                        if start_index < 0:
                            start_index += 1
                            break
                    return [start_index, end_index]
                elif nums[middle] < target:
                    left = middle + 1
                else:
                    right = middle - 1
            return [start_index, end_index]

    def searchRange2(self, nums, target):
        """
        :type nums: List[int]
        :type target: int
        :rtype: List[int]
        """
        nums_len = len(nums)
        start_index = -1
        end_index = -1
        if nums_len == 0:
            return [start_index, end_index]
        elif nums_len == 1:
            if nums[0] == target:
                return [0, 0]
            else:
                return [start_index, end_index]
        else:
            left = 0
            right = nums_len-1
            min = nums_len-1
            max = 0
            while left <= right:
                middle = (left + right) / 2
                if nums[middle] == target:
                    if middle < min:
                        min = middle
                    if middle > max:
                        max = middle
                    right -= 1
                elif nums[middle] < target:
                    left = middle + 1
                else:
                    right = middle - 1
            left = 0
            right = nums_len - 1
            while left <= right:
                middle = (left + right) / 2
                if nums[middle] == target:
                    if middle < min:
                        min = middle
                    if middle > max:
                        max = middle
                    left += 1
                elif nums[middle] < target:
                    left = middle + 1
                else:
                    right = middle - 1
            if min > max:
                return [-1, -1]
            else:
                return [min, max]