CODEWITHSUNDEEP
python
Ella
Ella

Reputation: 31

Python: 167 Leetcode Two SumII cannot work

I tried to solve Leetcode problem 167 as below, but it couldn't be accepted, I could run it successfully in Pycharm, I wonder what is the problem? Thanks! the question is:

Given an array of integers that is already sorted in ascending order, find two numbers such that they add up to a specific target number.

The function twoSum should return indices of the two numbers such that they add up to the target, where index1 must be less than index2. Please note that your returned answers (both index1 and index2) are not zero-based.

You may assume that each input would have exactly one solution and you may not use the same element twice.

Input: numbers={2, 7, 11, 15}, target=9 Output: index1=1, index2=2

and my code is:

class Solution(object):
def twoSum(self, numbers, target):

    for x in range(0,len(numbers)):
        for y in range(x+1,len(numbers)):
            if numbers[x]+numbers[y] == target:
                return x+1,y+1
    return x+1,y+1

Upvotes: 0

Views: 115

Answers (1)

tobias_k
tobias_k

Reputation: 82919

You are probably having a timeout issue. By testing each pair of numbers, your code has quadratic complexity, but once you have numbers[x], you know what numbers[y] ought to be, namely target - numbers[x], so you just need to check whether that number is in the list. To do this quickly, best convert the list to a dictionary mapping numbers to heir indices in the list.

numbers = [2, 7, 11, 15]
target = 9

d = {e: i for i, e in enumerate(numbers, 1)}
res = [(i, d[target-e]) for i, e in enumerate(numbers, 1) 
                        if target-e in d and d[target-e] > i]
print(res) # [(1, 2)]

Upvotes: 0

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