[LeetCode 287] Find the Duplicate Number - coder 进阶的专栏 - 博客频道 - CSDN.NET

[LeetCode 287] Find the Duplicate Number - coder 进阶的专栏 - 博客频道 - CSDN.NET

Given an array nums containing n + 1 integers where each integer is between 1 and n (inclusive), prove that at least one duplicate number must exist. Assume that there is only one duplicate number, find the duplicate one.

Note:

1. You must not modify the array (assume the array is read only).
2. You must use only constant, O(1) extra space.
3. Your runtime complexity should be less than O(n2).
4. There is only one duplicate number in the array, but it could be repeated more than once.

solution:

binary search, O(nlgn), get middle value, count number of value less than middle, if true search upper part, false to search lower part.

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