[leetcode: Python]167. Two Sum2 - Input array is sorted

最新推荐文章于 2025-09-09 20:07:09 发布

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最新推荐文章于 2025-09-09 20:07:09 发布

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分类专栏：算法文章标签： leetcode python

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本文介绍了一种在已排序的整数数组中寻找两个数使其和等于特定目标值的方法。提供两种算法实现，一种使用哈希表，另一种采用双指针技术。这两种方法均能有效地找到满足条件的两个数的下标。

题目：
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. Please note that 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.

Input: numbers={2, 7, 11, 15}, target=9
Output: index1=1, index2=2

方法一：性能49ms

class Solution:
    """
    @param numbers : An array of Integer
    @param target : target = numbers[index1] + numbers[index2]
    @return : [index1 + 1, index2 + 1] (index1 < index2)
    """
    def twoSum(self, numbers, target):
        # write your code here
        dict = {}
        for i in xrange(len(numbers)):
            x = numbers[i]
            if target - x in dict:
                return dict[target -x ] + 1, i + 1
            dict[x] = i

方法二：性能38ms

class Solution(object):
    def twoSum(self, numbers, target):
        """
        :type numbers: List[int]
        :type target: int
        :rtype: List[int]
        """
        i, j = 0, len(numbers)-1
        while True:
            s = numbers[i] + numbers[j]
            if s == target:
                return i+1, j+1
            elif s > target:
                j -= 1
            else:
                i += 1