풀이_LC167.md

💥 167. Two Sum II - Input array is sorted

• Date : 2021.06.27(일)
• Time : 25분

Problem

• Given an 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.
• Return the indices of the two numbers (1-indexed) as an integer array answer of size 2, where 1 <= answer[0] < answer[1] <= numbers.length.
• The tests are generated such that there is exactly one solution. You may not use the same element twice.

Constraints

• 2 <= numbers.length <= 3 * 10^4
• -1000 <= numbers[i] <= 1000
• numbers is sorted in non-decreasing order.
• -1000 <= target <= 1000
• The tests are generated such that there is exactly one solution.

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.

풀이

    def twoSum(self, numbers: list[int], target: int) -> list[int]:

        a = 0
        b = len(numbers)-1

        while a<b:
            if numbers[a] + numbers[b] == target:
                return [a+1, b+1]
            elif numbers[a] + numbers[b] > target:
                b = b-1
            else :
                a = a + 1

: 이 배열을 크기 순으로 정렬이 되어있는 배열이기 때문에 맨 앞과 맨 뒤를 좁혀가면서 더해가며 답을 찾는 방법으로 구현했다. 맨 앞과 맨 뒤를 기준으로 삼은 다음, 더한 값이 target보다 크냐 작냐에 따라 값을 빼주고 더해주고를 반복하였다.