532. K-diff Pairs in an Array LeetCode Solution

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Table of Contents

  1. Problem Statement
  2. Complexity Analysis
  3. K-diff Pairs in an Array solution in C++
  4. K-diff Pairs in an Array solution in Java
  5. K-diff Pairs in an Array solution in Python
  6. Additional Resources
532. K-diff Pairs in an ArrayLeetCode Solution image

Problem Statement of K-diff Pairs in an Array

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
i != j
|nums[i] – nums[j]| == k

Notice that |val| denotes the absolute value of val.

Example 1:

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:

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:

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

Constraints:

1 <= nums.length <= 104
-107 <= nums[i] <= 107
0 <= k <= 107

See also  446. Arithmetic Slices II - Subsequence LeetCode Solution

Complexity Analysis

  • Time Complexity: O(n)
  • Space Complexity: O(n)

532. K-diff Pairs in an Array LeetCode Solution in C++

class Solution {
 public:
  int findPairs(vector<int>& nums, int k) {
    int ans = 0;
    unordered_map<int, int> numToIndex;

    for (int i = 0; i < nums.size(); ++i)
      numToIndex[nums[i]] = i;

    for (int i = 0; i < nums.size(); ++i) {
      const int target = nums[i] + k;
      if (const auto it = numToIndex.find(target);
          it != numToIndex.cend() && it->second != i) {
        ++ans;
        numToIndex.erase(target);
      }
    }

    return ans;
  }
};
/* code provided by PROGIEZ */

532. K-diff Pairs in an Array LeetCode Solution in Java

class Solution {
  public int findPairs(int[] nums, int k) {
    int ans = 0;
    Map<Integer, Integer> numToIndex = new HashMap<>();

    for (int i = 0; i < nums.length; ++i)
      numToIndex.put(nums[i], i);

    for (int i = 0; i < nums.length; ++i) {
      final int target = nums[i] + k;
      if (numToIndex.containsKey(target) && numToIndex.get(target) != i) {
        ++ans;
        numToIndex.remove(target);
      }
    }

    return ans;
  }
}
// code provided by PROGIEZ

532. K-diff Pairs in an Array LeetCode Solution in Python

class Solution:
  def findPairs(self, nums: list[int], k: int) -> int:
    ans = 0
    numToIndex = {num: i for i, num in enumerate(nums)}

    for i, num in enumerate(nums):
      target = num + k
      if target in numToIndex and numToIndex[target] != i:
        ans += 1
        del numToIndex[target]

    return ans
 # code by PROGIEZ

Additional Resources

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