DAY1：leetcode #1 Two Sum

最新推荐文章于 2025-07-14 23:10:38 发布

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本文介绍了一种解决“两数之和”问题的算法实现，即从整数数组中找出两个数，使它们相加等于特定目标值，并返回这两个数的下标。通过筛选符合条件的数字并进行迭代计算来找到正确答案。

1、Two Sum

Given an array of integers, return indices of the two numbers such that they add up to a specific target.

You may assume that each input would have exactly one solution.

Example:

Given nums = [2, 7, 11, 15], target = 9,

Because nums[0] + nums[1] = 2 + 7 = 9,
return [0, 1].

UPDATE (2016/2/13):
The return format had been changed to zero-based indices. Please read the above updated description carefully.

class Solution(object):
    def twoSum(self, nums, target):
        """
        :type nums: List[int]
        :type target: int
        :rtype: List[int]
        """
        num_index=[]
        num_min=nums[0]
        for i in range(len(nums)):
            if nums[i] < num_min:
                num_min=nums[i]
        for i in range(len(nums)):
            if nums[i]+num_min <= target:
                num_index.append(i)
        for i in range(len(num_index)):
            for j in range(i+1,len(num_index)):
                if nums[num_index[i]] + nums[num_index[j]] == target:
                    return [num_index[i],num_index[j]]

这道题主要在于判断大小，把不符合条件的数字踢出去，然后迭代计算就可以了

---------------------------------------------2016.9.2 分割线-----------------------------------------------------

对于代码做了一些改进，多加了一些判断，整体时间仍不理想

class Solution(object):  
    def twoSum(self, nums, target):  
        """ 
        :type nums: List[int] 
        :type target: int 
        :rtype: List[int] 
        """  
        num_index = []  
        num_min = nums[0]
        num_max = nums[0]
        for i in range(len(nums)):  
            if nums[i] < num_min:  
                num_min = nums[i]
            if nums[i] > num_max:  
                num_max = nums[i]  
        for i in range(len(nums)):  
            if nums[i] + num_min <= target and nums[i] + num_max >= target:  
                num_index.append(i)  
        for i in range(len(num_index)):  
            for j in range(i+1,len(num_index)):  
                if nums[num_index[i]] + nums[num_index[j]] == target:  
                    return [num_index[i],num_index[j]]