A classic problem of hash set. The unordered_set of C++ is very suitable for this problem.
The code is as follows and it should be quite self-explanatory.
1 bool containsDuplicate(vector<int>& nums) { 2 unordered_set<int> st; 3 for (int i = 0; i < nums.size(); i++) { 4 if (st.find(nums[i]) != st.end()) 5 return true; 6 st.insert(nums[i]); 7 } 8 return false; 9 }
