Solution for exercise 1.3-7 in Introduction to Algorithms

最新推荐文章于 2022-09-13 01:31:35 发布

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本文介绍了一种在给定实数集合中寻找两数之和等于特定值x的算法。该算法首先对集合进行排序，然后对于集合中的每个元素a，使用二分查找判断x-a是否也在集合中。

Describe a θ(nlgn)-time algorithm that, given a set S of n real numbers and another real number x, determines whether or not there exist two elements in S whose sum is exactly x.

Solution:
First, sort the set using any θ(nlgn)-time sorting algorithm.
Then for each real number a in set S, search if (x-a) exists in the set S using binary seach algorithm.

It's easy to show that this solution is a θ(nlgn)-time algorithm.