leetcode——1——Two Sum

最新推荐文章于 2025-09-13 14:08:34 发布

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本文介绍了一种算法，用于在整数数组中找到两个数的索引，这两个数相加等于给定的目标值。该算法通过排序数组并使用双指针技巧实现效率。

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].

class Solution
{
    public:
    vector<int> twoSum(vector<int> &numbers, int target)
    {
       
        vector<int> num = numbers;
        std::sort(num.begin(), num.end());

        int length = numbers.size();
        int left = 0;
        int right = length - 1;
        int sum = 0;

        vector<int> index;

        while(left < right)
        {
            sum = num[left] + num[right];

            if(sum == target)
            {
                // find the index from the old array
                for(int i = 0; i < length; ++i)
                {
                    if(numbers[i] == num[left])
                    {
                        index.push_back(i);
                    }
                    else if(numbers[i] == num[right])
                    {
                        index.push_back(i);
                    }
                    if(index.size() == 2)
                    {
                        break;
                    }
                }
                break;
            }
            else if(sum > target)
            {
                --right;
            }
            else
            {
                ++left;
            }
        }

        return index;
    }
};