LoginPOTD #7 – Count pairs with given sum | Geeks For Geeks
Problem Statement
Geeks For Geeks – https://www.geeksforgeeks.org/problems/count-pairs-with-given-sum–150253/1
Given an array arr[] and an integer target. You have to find numbers of pairs in array arr[] which sums up to given target.
Input: arr[] = [1, 5, 7, -1, 5], target = 6 Output: 3 Explanation: Pairs with sum 6 are (1, 5), (7, -1) and (1, 5).
Input: arr[] = [1, 1, 1, 1], target = 2 Output: 6 Explanation: Pairs with sum 2 are (1, 1), (1, 1), (1, 1), (1, 1), (1, 1).
Input: arr[] = [10, 12, 10, 15, -1], target = 125 Output: 0
My Approach
Today’s problem is similar to Two Sum problem, but with a counter.
class Solution:
#Complete the below function
def countPairs(self,arr, target):
#Your code here
hash_count = {}
total_count = 0
for num in arr:
rem = target - num
if hash_count.get(rem):
total_count += hash_count.get(rem)
hash_count[num] = hash_count.get(num, 0) + 1
return total_count
