LeetCode.1.Two Sum

BishopTylaor

于 2018-03-20 18:09:49 发布

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分类专栏： LeetCode C++ python 文章标签：刷题 Python

本文链接：https://blog.youkuaiyun.com/github_37443078/article/details/79629546

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本文解析了经典的两数之和问题，提供了高效的解决方案。利用哈希表存储已遍历过的元素及其索引，实现快速查找。适用于C++及Python等语言。

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原题链接：Two Sum

题目内容：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, and you may not use the same element twice.
Example:

Given nums = [2, 7, 11, 15], target = 9,
Because nums[0] + nums[1] = 2 + 7 = 9,
return [0, 1].

C++

class Solution {
public:
    vector<int> twoSum(vector<int>& nums, int target) {
        std::unordered_map<int, int> temp_map;
        std::vector<int> res;
        for(int i = 0; i < nums.size(); i ++)
        {
            if(temp_map.count(target - nums[i]))
            {
                res.push_back(temp_map[target - nums[i]]); 
                res.push_back(i);
                break;
            }

            if(temp_map.count(nums[i]) != 1)
            {
                temp_map[nums[i]] = i;
            }
        }
        return res;
    }
};

Python

class Solution(object):
    def twoSum(self, nums, target):
        """
        :type nums: List[int]
        :type target: int
        :rtype: List[int]
        """
        res = dict()
        for i in range(0, len(nums)):
            if res.get(target - nums[i], None) == None: 
                res[nums[i]] = i
            else:
                return (res[target - nums[i]], i)