167. Two Sum II - Input array is sorted

167. Two Sum II - Input array is sorted

Easy

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.

Accepted 352,781 Submissions 669,308

0. 暴力搜索

1. 二分查找

class Solution:
    def twoSum(self, numbers: List[int], target: int) -> List[int]:
        # 有序数组的特性，首先就考虑二分查找
        # 时间复杂度O(nlogn)
        for i in range(len(numbers)):
            diff = target - numbers[i]
            # 设定左右边界，左边界从下一个数开始
            l = i + 1
            r = len(numbers) - 1
            while l<=r:
                mid = int(l + (r - l) / 2)
                if diff < numbers[mid]:
                    r = mid - 1
                elif diff > numbers[mid]:
                    l = mid + 1
                else:
                    return [i + 1, mid + 1]

3. 双指针

class Solution:
    def twoSum(self, numbers: List[int], target: int) -> List[int]:
        # 双指针
        # 时间复杂度O(n)
        i = 0
        j = len(numbers) - 1
        while i<j:
            if numbers[i] + numbers[j] == target:
                return [i + 1, j + 1]
            elif numbers[i] + numbers[j] > target:
                j -= 1
            elif numbers[i] + numbers[j] < target:
                i += 1

来源：CSDN

作者：authorized_keys

链接：https://blog.csdn.net/authorized_keys/article/details/104800018

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array