K-Diff Pairs In An Array Problem


Description

LeetCode Problem 532.

Given an array of integers nums and an integer k, return the number of unique k-diff pairs in the array. A k-diff pair is an integer pair (nums[i], nums[j]), where the following are true:

  • 0 <= i < j < nums.length
  • |nums[i] - nums[j]| == k Notice that |val| denotes the absolute value of val. Example 1:
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    Input: nums = [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:

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Input: nums = [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:

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Input: nums = [1,3,1,5,4], k = 0
Output: 1
Explanation: There is one 0-diff pair in the array, (1, 1).

Example 4:

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Input: nums = [1,2,4,4,3,3,0,9,2,3], k = 3
Output: 2

Example 5:

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Input: nums = [-1,-2,-3], k = 1
Output: 2

Constraints:

  • 1 <= nums.length <= 10^4
  • -10^7 <= nums[i] <= 10^7
  • 0 <= k <= 10^7


Sample C++ Code

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class Solution {
public:
    int findPairs(vector<int>& A, int k) {
        unordered_map<int, int> m;
        for (int n : A) m[n]++;
        int ans = 0;
        for (auto &[n, cnt] : m) {
            ans += k ? m.count(n - k) : cnt > 1;
        }
        return ans;
    }
};




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