Sword finger offer 03 Duplicate number in array

The finger of the sword Offer 03. Repeated numbers in an array

Address of force deduction problem solution
The difficulty is simple 695

Find the repeated numbers in the array .

At a length of n Array of nums All the numbers in 0～n-1 Within the scope of . Some numbers in the array are repeated , But I don't know how many numbers are repeated , I don't know how many times each number has been repeated . Please find any duplicate number in the array .

Example 1：

 Input ：
[2, 3, 1, 0, 2, 5, 3]
 Output ：2  or  3 

analysis

Declaration set , Determine whether the elements added to the collection are duplicate elements

Code

class Solution {
    public int findRepeatNumber(int[] nums) {
        Set<Integer> set=new HashSet<Integer>();
        int repeat=-1;
        for(int num:nums){
            if(!set.add(num)){
                repeat=num;
                break;
            }
        }
    return repeat;
    }
}