Find the Duplicate Number

Find the Duplicate Number

Given an array of integers nums containing n + 1 integers where each integer is in the range [1, n] inclusive, there is only one repeated number in nums. Return this repeated number.

You must solve it without modifying the array nums and using only constant extra space.

Examples

Example 1:

Input: nums = [1, 3, 4, 2, 2]
Output: 2

Example 2:

Input: nums = [3, 1, 3, 4, 2]
Output: 3

Example 3:

Input: nums = [3, 3, 3, 3, 3]
Output: 3

Constraints

• 1 <= n <= 10^5
• nums.length == n + 1
• 1 <= nums[i] <= n
• There is only one repeated number in nums, but it could be repeated more than once.

Expected Complexity

• Time: O(n)
• Space: O(1)