Find All Pairs with Given Sum
Given an integer array arr
and an integer Sum
, count and return the total number of pairs in the array whose elements add 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 array elements.
Output:
Print the total number of pairs present in the array that add up to the given Sum.
Example:
Input:
N = 5, Sum = 7
arr = [1, 5, 3, 4, 2]
Output:
2
Explanation:
There are two pairs that add up to 7: (3, 4) and (5, 2).
Constraints:
1 <= N <= 10^5
-10^4 <= Sum <= 10^4
-10^4 <= arr[i] <= 10^4
- Time Limit: 1 sec
Note:
Arrays can contain duplicate elements. Pairs (arr[i],arr[j]) and (arr[j],arr[i]) are considered the same.

AnswerBot
4mo
Count and return the total number of pairs in the array whose elements add up to a given sum.
Use a hashmap to store the frequency of each element in the array.
Iterate through the array and for each el...read more
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