Frontend Developer Intern

You are given an array/list ‘ARR’ consisting of ‘N’ distinct integers arranged in ascending order. You are also given an integer ‘TARGET’. Your task is to count all the distinct pairs in ‘ARR’ such that their sum is equal to ‘TARGET’.

Note:

1. Pair (x,y) and Pair(y,x) are considered as the same pair. 

2. If there exists no such pair with sum equals to 'TARGET', then return -1.

Example:

Let ‘ARR’ = [1 2 3] and ‘TARGET’ = 4. Then, there exists only one pair in ‘ARR’ with a sum of 4 which is (1, 3). (1, 3) and (3, 1) are counted as only one pair.

You are given a string 'STR' containing lowercase English letters from a to z inclusive. Your task is to find all non-empty possible subsequences of 'STR'.

A Subsequence of a string is the one which is generated by deleting 0 or more letters from the string and keeping the rest of the letters in the same order.