
Count Pairs with Given Sum
Given an integer array/list arr
and an integer 'Sum', determine the total number of unique pairs in the array whose elements sum up to the given 'Sum'.
Input:
The first line contains two space-separated integers, N and Sum.
The second line contains N space-separated integers representing the elements of the array.
Output:
Output a single integer, representing the total number of pairs whose sum is equal to 'Sum'.
Example:
Input:
5 7
1 2 3 4 3
Output:
2
Constraints:
1 ≤ N ≤ 105
-104 ≤ Sum ≤ 104
-104 ≤ arr[i] ≤ 104
- Time Limit: 1 sec
Note:
Array may contain duplicate elements.
The pairs (arr[i], arr[j]) and (arr[j], arr[i]) are considered the same.

AnswerBot
5d

Count the total number of unique pairs in an array whose elements sum up to a given value.
Use a hashmap to store the frequency of each element in the array.
Iterate through the array and for each eleme...read more

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