Contains Duplicate II

class Solution {
public:
bool containsNearbyDuplicate(vector<int>& nums, int k) {
int size=nums.size();
map<int,int> mymap;
int start=0;
int end=0;
if(k==0)
return false;
for(int i=0;i<size;i++)
{
if(end-start>k)
{
mymap.erase(nums[start]);
start++;
}
if(mymap.find(nums[i])==mymap.end())
{
mymap.insert(pair<int,int>(nums[i],1));
end++;
}
else
return true;
}
return false;
}
};