//73
class Solution {
public:
vector<int> findNumsAppearOnce(vector<int>& nums) {
vector<int> ans;
unordered_map<int, int> hash;
for (auto x : nums)
hash[x]++;
for (auto x : nums)
if (hash[x] == 1)
ans.push_back(x);
return ans;
}
};