Two Sum
class Solution {
public:
vector<int> twoSum(vector<int>& nums, int target) {
unordered_map<int,int> map;
vector<int> res;
if(nums.empty())
return res;
for(int i=0;i<nums.size();i++){
if(map.find(target-nums[i])==map.end()){
map[nums[i]]=i;
}
else{
res.push_back(map[target-nums[i]]);
res.push_back(i);
return res;
}
}
}
};
