运用hash表
class Solution {
public:
vector<int> twoSum(vector<int>& nums, int target) {
unordered_map<int, int> hash;
vector<int> result;
for (int i=0; i<nums.size(); i++) {
int numToFind = target - nums[i];
if (hash.find(numToFind)!=hash.end()) {
result.push_back(hash[numToFind]);
result.push_back(i);
}
hash[nums[i]] = i;
}
return result;
}
};
