LeetCode | Two Sum

最新推荐文章于 2021-07-09 20:17:22 发布

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本文介绍了一种解决两数之和问题的高效算法。给定一个整数数组及目标值，找出数组中和为目标值的两个数的索引。算法使用了有序映射来辅助查找，确保每个元素只被使用一次。

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].

class Solution {
public:
    vector<int> twoSum(vector<int>& nums, int target) {

    int res1 = 0, res2 = 0;
    multimap<int,int> m;
    multimap<int,int>::iterator it;
    multimap<int,int>::iterator it2;
    vector<int> res;

    for(int i=0;i<nums.size();i++)
    {
        m.insert(make_pair(nums[i],i));
    }

    it2 = m.begin();
    for(int i=0;i<nums.size();i++)
    {
        if(it2->first > target/2)
            break;
        it = m.find(target-it2->first);
        if(it!=m.end() && it!=it2)
        {
            res1 = it->second;
            res2 = it2->second;
            break;
        }
        it2++;
    }
    if(res1 > res2)
        swap(res1,res2);

    res.push_back(res1);
    res.push_back(res2);
    return res;


    }
};