Contains Duplicate

Given an array of integers, find if the array contains any duplicates. Your function should return true if any value appears at least
twice in the array, and it should return false if every element is distinct.

class Solution {
public:
bool containsDuplicate(vector<int>& nums) {
int n=nums.size();
if(n==0||n==1)return false; //数组为空或者0时，返回 false
int flag=0;
sort(nums.begin(),nums.end());
for(int i=0;i<n;i++)
if(nums[i]==nums[i+1]){
flag=1;
break;
}
if(flag==1)return true;
else return false;
}
};