class Solution {
public:
vector<int> twoSum(vector<int>& nums, int target) {
vector<int> result;
if(nums.size()<2)
return result;
unordered_map<int ,int> m;
for(int i=0; i<nums.size(); i++)
{
auto iter = m.find(target-nums[i]);
if(iter != m.end())
{
result.push_back(iter->second);
result.push_back(i);
break;
}
m[nums[i]] = i;
}
return result;
}
};