与关联容器相关的模板类型,包含两个数据成员,在utility头文件中定义。
类模板:template
参数:T1是第一个值的数据类型,T2是第二个值的数据类型。
功能:pair将一对值组合成一个值,这一对值可以具有不同的数据类型(T1和T2),两个值可以分别用pair的两个公有函数first和second访问。
utility
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