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  1. # your code goes here
  2. n=int(input())
  3. target=int(input())
  4. arr=list(map(int, input().split()))
  5. hashmap={}
  6. ctr=0
  7. for x in arr:
  8. 	req=target-x
  9. 	if req in hashmap:
  10. 		ctr+=hashmap[req]
  11. 	hashmap[x]=hashmap.get(x, 0)+1
  12. print(ctr)
  13.  
Success #stdin #stdout 0.08s 14112KB
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https://ideone.com/l0PP8Q
count of pairs whose sum is k( hashmap solution)
language:
Python 3 (python  3.12)
created:
11 hours ago
visibility:
public

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