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Python List Comprehension to find pair with given sum from two arrays

  • Difficulty Level : Easy
  • Last Updated : 21 Nov, 2018

Given two unsorted arrays of distinct elements, the task is to find all pairs from both arrays whose sum is equal to x.

Examples:

Input :  arr1 = [-1, -2, 4, -6, 5, 7]
         arr2 = [6, 3, 4, 0]  
         x = 8
Output : [(5, 3), (4, 4)]
         

Input : arr1 = [1, 2, 4, 5, 7] 
        arr2 = [5, 6, 3, 4, 8]  
        x = 9
Output : [(1, 8), (4, 5), (5, 4)]

We have existing solution for this problem please refer Given two unsorted arrays, find all pairs whose sum is x link. We can solve this problem quickly in python using List comprehension. Approach is very simple, we will consider all those pairs for which if k lies in arr2 then x-k should lie in arr1, so pair will be (x-k,k).




# Function to find all pairs whose sum is x in 
# two arrays
  
def allPairs(arr1,arr2,x):
       
     # finds all pairs in two arrays
     # whose sum is x
     print ([(x-k,k) for k in arr2 if (x-k) in arr1])
  
# Driver program
if __name__ == "__main__":
    arr1 = [-1, -2, 4, -6, 5, 7]
    arr2 = [6, 3, 4, 0]  
    x = 8
    allPairs(arr1,arr2,x)

Complexity : O(n*n)
Output:

[(5, 3), (4, 4)]

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