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.

Question

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:

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.

Accepted Answer

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 with the sum equal to 'TARGET'.