Contains Duplicate ii

class Solution {
public:
    bool containsNearbyDuplicate(vector<int>& nums, int k) {

        unordered_map<int,int> m;
        int n = nums.size();

        for(int i  = 0 ;i <n; i++){

            if(m.find(nums[i])==m.end()){
                m.insert({nums[i], i});
            }
            else{

               int storedIndex = m.find(nums[i])->second;

                if(i-storedIndex<=k){
                    return true;
                }
                else{
                    m.find(nums[i])->second = i;
                }

            }

        }


        return false;

    }
};