Two Sum

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].

The return format had been changed to zero-based indices. Please read the above updated description carefully.

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

if(nums.size()<2)
{
return ret;
}

for(int i=0; i<nums.size(); ++i)
{
int needed = target - nums[i];
if(visitedMap.find(needed)!=visitedMap.end())
{
ret.push_back(visitedMap[needed]);
ret.push_back(i);
return ret;
}
visitedMap.insert(pair<int, int>(nums[i], i) );
}
return ret;
}
};