The front() function returns a reference to the first element of the vector, and runs in constant time.
For example, the following code uses a vector and the sort() algorithm to display the first word (in alphabetical order) entered by a user:
vector<string> words; string str; while( cin >> str ) words.push_back(str); sort( words.begin(), words.end() ); cout << "In alphabetical order, the first word is '" << words.front() << "'." << endl;
When provided with this input:
now is the time for all good men to come to the aid of their country
...the above code displays:
In alphabetical order, the first word is 'aid'.