The C++ STL tutorial

The C++ STL tutorial

In the previous sections, we've already learned the concept of a C++ template. The C++ STL (Standard Template Library) is a powerful set of C++ template classes that provide common template classes and functions that enable a variety of popular and commonly used algorithms and data structures, such as vectors, lists, queues, and stacks.

The core of the C++ standard template library consists of three components:

All three components come with rich predefined functions that help us handle complex tasks in a simple way.

The following program demonstrates a vector container (a template for the C++ standard), which is very similar to an array, but the only difference is that the vector automatically handles its own storage needs when it needs to scale up:

#include <iostream>
#include <vector>
using namespace std;
 
int main()
{
   // 创建一个向量存储 int
   vector<int> vec; 
   int i;

   // 显示 vec 的原始大小
   cout << "vector size = " << vec.size() << endl;

   // 推入 5 个值到向量中
   for(i = 0; i < 5; i++){
      vec.push_back(i);
   }

   // 显示 vec 扩展后的大小
   cout << "extended vector size = " << vec.size() << endl;

   // 访问向量中的 5 个值
   for(i = 0; i < 5; i++){
      cout << "value of vec [" << i << "] = " << vec[i] << endl;
   }

   // 使用迭代器 iterator 访问值
   vector<int>::iterator v = vec.begin();
   while( v != vec.end()) {
      cout << "value of v = " << *v << endl;
      v++;
   }

   return 0;
}

When the above code is compiled and executed, it produces the following results:

vector size = 0
extended vector size = 5
value of vec [0] = 0
value of vec [1] = 1
value of vec [2] = 2
value of vec [3] = 3
value of vec [4] = 4
value of v = 0
value of v = 1
value of v = 2
value of v = 3
value of v = 4

There are a few things to note about the various functions used in the example above:

• push_back () member function inserts a value at the end of the vector and expands the size of the vector if necessary.
• The size () function shows the size of the vector.
• The begin () function returns an iterator that points to the beginning of the vector.
• The end() function returns an iterator that points to the end of the vector.