167.twoSum2.py

# Given a 1-indexed array of integers numbers that is already sorted in non-decreasing order, find two numbers such that they add up to a specific target number. Let these two numbers be numbers[index1] and numbers[index2] where 1 <= index1 < index2 <= numbers.length.

# Return the indices of the two numbers, index1 and index2, added by one as an integer array [index1, index2] of length 2.

# The tests are generated such that there is exactly one solution. You may not use the same element twice.

# Your solution must use only constant extra space.


# Example 1:
#
# # Input: numbers = [2,7,11,15], target = 9
# Output: [1,2]
# # Explanation: The sum of 2 and 7 is 9. Therefore, index1 = 1, index2 = 2. We return [1, 2].
# # Example 2:
#
# # Input: numbers = [2,3,4], target = 6
# Output: [1,3]
# # Explanation: The sum of 2 and 4 is 6. Therefore index1 = 1, index2 = 3. We return [1, 3].
# # Example 3:
#
# Input: numbers = [-1,0], target = -1
# Output: [1,2]
# Explanation: The sum of -1 and 0 is -1. Therefore index1 = 1, index2 = 2. We return [1, 2].
#
from typing import List


class Solution:
    def twoSum(self, numbers: List[int], target: int) -> List[int]:
        # tow pointers
        l, r = 0, len(numbers) - 1

        while l < r:
            cur_cum = numbers[l] + numbers[r]

            if cur_cum > target:
                r -= 1
            elif cur_cum < target:
                l += 1
            else:
                return [l + 1, r + 1]

        # if we can't find a pair, return empty list
        return []