0010 - Two Sum II Input Array Is Sorted

Given an array of integers numbers that is sorted in non-decreasing order.

Return the indices (1-indexed) of two numbers, [index1, index2], such that they add up to a given target number target and index1 < index2. Note that index1 and index2 cannot be equal, therefore you may not use the same element twice.

There will always be exactly one valid solution.

Your solution must use O ( 1 ) O(1) additional space.

Example 1:

Input: numbers = [1,2,3,4], target = 3

Output: [1,2] Explanation: The sum of 1 and 2 is 3. Since we are assuming a 1-indexed array, index1 = 1, index2 = 2. We return [1, 2].

In [2]:

def twosum(nums,target):
    l,r=0,len(nums)-1
    while l<r:
        total=nums[l]+nums[r]
        if total==target:
            return [nums[l],nums[r]]
        elif total>target:
            r-=1
        else:
            l+=1

In [4]:

print(twosum([1,2,3,4],3))

[1, 2]