Container constructors
Syntax:
#include <list> container(); container( const container& c ); container( size_type num, const TYPE& val = TYPE() ); container( input_iterator start, input_iterator end ); ~container(); The default list constructor takes no arguments, creates a new instance of that list. The second constructor is a default copy constructor that can be used to create a new list that is a copy of the given list c. The third constructor creates a list with space for num objects. If val is specified, each of those objects will be given that value. For example, the following code creates a vector consisting of five copies of the integer 42: vector<int> v1( 5, 42 ); The last constructor creates a list that is initialized to contain the elements between start and end. For example: // create a vector of random integers cout << "original vector: "; vector<int> v; for( int i = 0; i < 10; i++ ) { int num = (int) rand() % 10; cout << num << " "; v.push_back( num ); } cout << endl; // find the first element of v that is even vector<int>::iterator iter1 = v.begin(); while( iter1 != v.end() && *iter1 % 2 != 0 ) { iter1++; } // find the last element of v that is even vector<int>::iterator iter2 = v.end(); do { iter2--; } while( iter2 != v.begin() && *iter2 % 2 != 0 ); cout << "first even number: " << *iter1 << ", last even number: " << *iter2 << endl; cout << "new vector: "; vector<int> v2( iter1, iter2 ); for( int i = 0; i < v2.size(); i++ ) { cout << v2[i] << " "; } cout << endl; When run, this code displays the following output: original vector: 1 9 7 9 2 7 2 1 9 8 first even number: 2, last even number: 8 new vector: 2 7 2 1 9 All of these constructors run in linear time except the first, which runs in constant time. The default destructor is called when the list should be destroyed. |