LintCode 61. Search for a Range

最新推荐文章于 2022-03-09 14:08:35 发布

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最新推荐文章于 2022-03-09 14:08:35 发布

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分类专栏： OJ-LintCode 算法-二分搜索

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算法-二分搜索

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这是一篇关于如何在有序数组中使用二分搜索法找到给定目标值起始和结束位置的博客。当目标值不存在于数组中时，返回[-1, -1]。文章提出了挑战，要求在O(log n)的时间复杂度内完成。" 110933490,10294218,Python中使用NumPy和Pandas计算Pearson相关系数,"['Python', '数据分析', '相关系数', 'Pandas库', 'NumPy库']

题目

Given a sorted array of n integers, find the starting and ending position of a given target value.
If the target is not found in the array, return [-1, -1].
Have you met this question in a real interview?
Yes
Example
Given [5, 7, 7, 8, 8, 10] and target value 8,
return [3, 4].
Challenge
O(log n) time.
Tags
Array Sorted Array Binary Search

思路

两遍二分搜索。

代码

class Solution:
    """
    @param: A: an integer sorted array
    @param: target: an integer to be inserted
    @return: a list of length 2, [index1, index2]
    """
    def searchRange(self, A, target):
        # write your code here
        left = -1; right = -1
        start = 0; end = len(A) - 1
        while start <= end:
            mid = start + (end - start) // 2
            if A[mid] == target:
                left = mid
                end = mid - 1
            elif A[mid] < target:
                start = mid + 1
            else:
                end = mid - 1
        start = 0; end = len(A) - 1
        while start <= end:
            mid = start + (end - start) // 2
            if A[mid] == target:
                right = mid
                start = mid + 1
            elif A[mid] < target:
                start = mid + 1
            else:
                end = mid - 1
        return [left, right]