Contains Duplicate II

Description:

Given an array of integers and an integer k, find out whether there 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.

Code:

 1  bool containsNearbyDuplicate(vector<int>& nums, int k) {
 2         unordered_map<int,int>m;
 3         int n = nums.size();
 4         for (int i = 0; i < n; ++i)
 5         {
 6             if ( m.count(nums[i]) && i - m[nums[i]] <= k)
 7                 return true;
 8             else
 9                 m[nums[i]] = i;
10         }
11         return false;
12     }