[leetCode]1. Two Sum（自学留存）

原创于 2018-02-25 15:55:55 发布 · 147 阅读

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本文介绍了一种解决两数之和问题的高效算法。通过使用map存储数组元素及其索引，实现快速查找目标和补数的过程。此方法避免了传统双重循环带来的高时间复杂度，显著提升了求解效率。

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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].

Personal tips:使用map key-value查找比数组高效。代码如下：

class Solution {
public:
	vector<int> twoSum(vector<int>& nums, int target) {
		int m = nums.size(); vector<int> sum{};
		map<int, int> num;
		for (int i = 0; i < m; ++i)
		{
			if (num.count(target - nums[i]))
			{	
				sum.push_back(num[target - nums[i]]);
				sum.push_back(i);
				return sum;
			}
			num.insert(pair<int, int>(nums[i], i));
		}
	}
};