Contains Duplicate

class Solution {
public:
bool containsDuplicate(vector<int>& nums) {
int n=nums.size();
if(n==0)
return 0;
int i;
map<int,int> mp;
for(i=0;i<n;i++)
{
if(mp[nums[i]]==0)
mp[nums[i]]=1;
else
return 1;
}
return 0;
}
};