[文学研究]数据结构与程序设计教师鲍钰.ppt

数据结构与程序设计 教师：鲍钰 数据结构与程序设计(7) 教师：鲍钰 ybao@sei.ecnu.edu.cn 第四章 Linked Stacks and Queues 问题的提出 P113 引入指针 Figure 4.1 指针声明 C++ uses an asterisk * to denote a pointer. If Item is a type, then a pointer to such an Item object has the type Item *. For example, Item *item_ptr; declares item_ptr as a pointer variable to an Item object. Creating dynamic objects Item_ptr = new Item; creates a new dynamic object of type Item and assigns its location to the pointer variable item_ptr. Deleting dynamic objects delete item_ptr; disposes of the dynamic object to which item_ptr points and returns the space it occupies to the free store so it can be used again. Following pointers *item_ptr denotes the object to which item_ptr points. NULL pointers If a pointer variable item_ptr has no dynamic object to which it currently refers, then it should be given the special value. Item_ptr = NULL; Uninitialized or random pointer objects should always be reset to NULL. After deletion, a pointer object should be reset to NULL. #includeiostream.h Dynamically Allocated Arrays Item_array = new Item[array_size]; creates a dynamic array of Item objects, indexed from 0 up to array_size ? 1. Dynamically Allocated Arrays for example: int size, *dynamic_array, i; cout Enter an array size: ; cin size; dynamic_array = new int[size]; for (i = 0; i size; i++) dynamic_array[i] = i; Dynamically Allocated Arrays Dynamically Allocated ArraysP120 Dynamically Allocated Arrays delete [] dynamic_array; returns the storage in dynamic array to the free store. 指针运算 If i is an integer value and p is a pointer to an Item, then p + i is an expression of type Item *. The value of p + i gives the memory address offset from p by i Item objects. That is, the expression p + i actually yields the address p + n*i, where n is the number of bytes of storage occupied by a simple object of type Item. Addresses of automatic objects If x is a variable of type Item, then x is a value of type Item * that gives the ad