public class Solution
extends Object
287 - Find the Duplicate Number\.
Medium
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 the problem **without** modifying the array `nums` and uses only constant extra space.
**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 = [1,1]
**Output:** 1
**Example 4:**
**Input:** nums = [1,1,2]
**Output:** 1
**Constraints:**
* 1 <= n <= 105
* `nums.length == n + 1`
* `1 <= nums[i] <= n`
* All the integers in `nums` appear only **once** except for **precisely one integer** which appears **two or more** times.
**Follow up:**
* How can we prove that at least one duplicate number must exist in `nums`?
* Can you solve the problem in linear runtime complexity?