how to sum two numbers in a list?

Question

what is the solution of this by python 3 ?

Given an array of integers, return indices of the two numbers such that they add up to a spe

Answer 1

We can use to pointers, at the beginning and at the end of the list to check each index by the sum of the two numbers, looping once.

def sumOfTwo(array, target):
    i = 0
    j = len(array) - 1
    while i < j:
      add = array[i] + array[j]
      if add == target:
        return True
      elif add < target:
        i += 1
      else:
        j -= 1
    return False 

input -> [1, 2, 3, 4] -> target: 6

 i->    <-j
[1][2][3][4]  if i + j = target return True 
              if i + j < target increase i
              else decrease j

Note: In a edge case, a guard of check before the loop, in case: target is a negative value, list is empty, target is null.