287 - Find the Duplicate Number

class Solution {
    public int findDuplicate(int[] nums) {
        int i=0;
        while(i<nums.length)
        {
            int correct=nums[i]-1;
            if(i<nums.length && nums[i]!=nums[correct])
            {
                 int swap=nums[i];
                nums[i]=nums[correct];
                nums[correct]=swap;
            }
            else 
            {
                i++;
            }
        }
        for(int j=0;j<nums.length;j++)
        {
            if(nums[j]!=j+1)
            {
                return nums[j];
            }
        }
        return nums.length;
    }
}