Counting steps · routine

A pair in a sorted list

nums is sorted. Write has_pair(nums, target) returning True if two different positions hold numbers adding up to target.

Start one finger at each end. Too small? Move the left finger right. Too big? Move the right finger left. Each step rules out one number for good.

right answers
arguments left as they should be
fast enough at scale

def has_pair(nums, target):
    for i in range(len(nums)):
        for j in range(i + 1, len(nums)):
            if nums[i] + nums[j] == target:
                return True
    return False

Run adds print(has_pair([1, 2, 4, 7], 9)) after your code, to try it.

Stuck on the idea rather than the code? The Two pointers and formulas lesson walks through it.