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 a sorted array that sum up to a given target value, returning -1 if no pairs exist.

Two-Pointer Technique: Use two pointers, one at the start and one at the end of the array, to find pairs efficiently.
Distinct Elements: Since the array contains distinct integers, each valid pair will be unique.
Example: For ARR = [1, 2, 3] and TARGET = 4, the only pair is (1, 3).
Return Value: If pairs are found, return the count; otherwise, return -1.

Asked in EX Squared Solutions