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
     
      & nums, int k) { 2         unordered_map
      
       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     }