Approach-1 Find Duplicates (Sort and find)

find_duplicates_app_1.cpp

class Solution {
public:
    int findDuplicate(vector<int>& nums) {
        sort(nums.begin(), nums.end());
        for (int i = 1; i < nums.size(); i++) {
            if (nums[i] == nums[i - 1])
                return nums[i];
        }
        return -1;
    }
};