287. Find the Duplicate Number

很简单

class Solution {public:    int findDuplicate(vector<int>& nums) {        if(nums.size()<=1)            return 0;        sort(nums.begin(),nums.end());        for(int i=1;i<nums.size();i++)        {            if(nums[i]==nums[i-1])                return nums[i-1];        }        return 0;    }};