167. Two Sum II – Input array is sorted

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.

Note:

• 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.

Example:

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.

# -*- coding: utf-8 -*-
"""
Created on Wed Mar  6 09:46:09 2019

@author: zhuli02
"""

class Solution(object):
    def twoSum(self, numbers, target):
        """
        :type numbers: List[int]
        :type target: int
        :rtype: List[int]
        """
        left = 1
        right = len(numbers)
        while left<right:
            a = numbers[left-1]
            b = numbers[right-1]
            s = a + b
            if s == target:
                new_list = [left, right]
                return new_list
            elif s < target:
                left += 1
                continue
            elif s > target:
                right -= 1
                continue