two sum

class Solution {
public:
vector<int> twoSum(vector<int> &numbers, int target) {
vector<int> ret(2,-1);
unordered_map<int, int> m;    //value->index map
for(int i = 0; i < numbers.size(); i ++)
{
if(m.find(target-numbers[i]) == m.end())
//target-numbers[i] not appeared
m[numbers[i]] = i;
else
{
ret[0] = m[target-numbers[i]]+1;
ret[1] = i+1;
return ret;
}
}
}
};