Pair Sum Problem Statement

You are provided with an array ARR consisting of N distinct integers in ascending order and an integer TARGET. Your objective is to count all the distinct pairs in ARR whose sum equals TARGET.

Note:

  • Pair (x, y) and Pair (y, x) are considered as the same pair.
  • If no such pair exists with a sum equal to 'TARGET', then return -1.

Example:

Input:
ARR = [1, 2, 3], TARGET = 4
Output:
1
Explanation:

There exists only one pair in ARR with a sum of 4, which is (1, 3). (1, 3) and (3, 1) are counted as a single pair.

Constraints:

  • 1 ≤ T ≤ 100
  • 2 ≤ N ≤ 5000
  • 1 ≤ ARR[i], TARGET ≤ 105
  • The array ARR contains distinct elements.
AnswerBot
4mo

Count distinct pairs in an array whose sum equals a given target.

  • Use two pointers approach to find pairs efficiently.

  • Keep track of visited elements to avoid duplicates.

  • Return -1 if no such pair exists...read more

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