【LeetCode】Two Sum

Two Sum

Given an array of integers, find two numbers such that they add up to a specific target number.

The function twoSum should return indices of the two numbers such that they add up to the target, where index1 must be less than index2. Please note that your returned answers (both index1 and index2) are not zero-based.

You may assume that each input would have exactly one solution.

Input: numbers={2, 7, 11, 15}, target=9
Output: index1=1, index2=2

用map<value, index>

遍历numbers，在map中寻找target-numbers[i].

若找到则结束，若找不到则将numbers[i]加入map

class Solution {
public:
    map<int,int> m;
    vector<int> twoSum(vector<int> &numbers, int target) 
    {
        vector<int> v;
        for(vector<int>::size_type st = 0; st < numbers.size(); st ++)
        {
            map<int,int>::iterator it = m.find(target-numbers[st]);
            if(it == m.end())
                m.insert(map<int,int>::value_type(numbers[st], st+1));
            else
            {
                v.push_back(it->second);
                v.push_back(st+1);
                return v;
            }
        }
    }
};

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【LeetCode】Two Sum

原文：http://www.cnblogs.com/ganganloveu/p/3728849.html