1.简介

 

Pair与Tuple都是标准库提供的通用工具，主要用来组合两个或者多个值。

 

2.Pair

 

Pair可以由<utility>引入，定义在bits/stl_pair.h中

 /**
   *  @brief Struct holding two objects of arbitrary type.
   *
   *  @tparam _T1  Type of first object.
   *  @tparam _T2  Type of second object.
   */
  template<typename _T1, typename _T2>
    struct pair
    : private __pair_base<_T1, _T2>
    {
      typedef _T1 first_type;    /// @c first_type is the first bound type
      typedef _T2 second_type;   /// @c second_type is the second bound type

      _T1 first;                 /// @c first is a copy of the first object
      _T2 second;   
    }

 

2.1 默认构造函数

 

pair<T1,T2> p：默认构造函数，建立一个pair，其元素类型分别为T1和T2，各自以其default默认构造函数初始化

#include <iostream>
#include <utility>

u