LeetCode - 532. K-diff Pairs in an Array

532. K-diff Pairs in an Array - easy

문제

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.

제한사항

• The pairs (i, j) and (j, i) count as the same pair.
• The length of the array won’t exceed 10,000.
• All the integers in the given input belong to the range: [-1e7, 1e7].

입출력 예

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).

풀이

• hash

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