leetcode 219. Contains Duplicate II

Given an array of integers and an integer k,
find out whether there are two distinct indices i and j in
the array such that nums[i] = nums[j]and
the difference between i and j is
at most k.

Map:

class Solution {
public:
bool containsNearbyDuplicate(vector<int>& nums, int k) {
map<int, int> mp;
map<int, int>::iterator it = mp.end();
for(int i= 0; i < nums.size(); i++){
it = mp.find(nums[i]);
if(it != mp.end()){
if(abs(it->second - i) <= k) return true;
else mp[nums[i]] = i;
}else{
mp[nums[i]] = i;
}
}
return false;
}
};