1. Two Sum（leetcode）

1. Two Sum

 

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• Total Accepted: 267356
• Total Submissions: 1058783
• Difficulty: Easy

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.

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解析：

key-value，map做法，简单，熟悉了一下leetcode的提交格式。

ac代码：

class Solution {
public:
    vector<int> twoSum(vector<int> &numbers, int target) {
        vector<int> result;
        map<int, int> m;
        if (numbers.size() < 2)
            return result;
        for (int i = 0; i < numbers.size(); i++)
            m[numbers[i]] = i;


        map<int, int>::iterator it;
        for (int i = 0; i < numbers.size(); i++) {
            if ((it = m.find(target - numbers[i])) != m.end())
            {
                if (i == it->second) continue;
                result.push_back(i);
                result.push_back(it->second);
                return result;
            }
        }
        return result;
    }
};