LeetCode-in-All

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:

Follow up:

Solution

class Solution {
    func findDuplicate(_ nums: [Int]) -> Int {
        let n = nums.count
        var array = [Bool](repeating: false, count: n)
        for num in nums {
            if array[num] {
                return num
            }
            array[num] = true
        }
        return n
    }
}