LeetCode : K-diff Pairs in an Array

Given an array of integers and an integer k, you need to find the number of unique k-diff pairs in the array. Here a k-diff pair is defined as an integer pair (i, j), where i and j are both numbers in the array and their absolute difference is k.

Example 1:
Input: [3, 1, 4, 1, 5], k = 2
Output: 2
Explanation: There are two 2-diff pairs in the array, (1, 3) and (3, 5).
Although we have two 1s in the input, we should only return the number of unique pairs.
Example 2:
Input:[1, 2, 3, 4, 5], k = 1
Output: 4
Explanation: There are four 1-diff pairs in the array, (1, 2), (2, 3), (3, 4) and (4, 5).
Example 3:
Input: [1, 3, 1, 5, 4], k = 0
Output: 1
Explanation: There is one 0-diff pair in the array, (1, 1).

class Solution {
public:
    int findPairs(vector<int>& nums, int k) {
        unordered_map<int,int>m;
         int res = 0;
         for(int i=0;i<nums.size();++i){
             m[nums[i]]++;
         }
         for(auto a:m){
             if(k==0&&a.second>1)
                ++res;
              if(k>0&&m.count(a.first+k))
                ++res;
         }
        return res;
    }
};