LeetCode:167. Two Sum II - Input array is sorted

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题目概述

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:

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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.

简单题，由于数组是递增的，所以一开始假定index1为0，index2为数组的最后一个索引，如果对应的两个数相加比target小，则让index1加一，反之让index2减1，直到找到两个和为target的值的索引

最后注意把求得的index+1即可。

代码实现

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class Solution:
    def twoSum(self, numbers: 'list[int]', target: 'int') -> 'list[int]':
        index1 = 0
        index2 = len(numbers) - 1

        while numbers[index1] + numbers[index2] != target:
            if numbers[index1] + numbers[index2] > target:
                index2 -= 1
            else:
                index1 += 1

        return [index1+1, index2+1]