//

// Created by zing on 6/1/2020.

//

#include <iostream>

using namespace std;

void define() {

//1、指针的定义

int a = 10; //定义整型变量a

//指针定义语法： 数据类型 * 变量名 ;

int *p;

//指针变量赋值

p = &a; //指针指向变量a的地址

cout << &a << endl; //打印数据a的地址

cout << p << endl; //打印指针变量p

//2、指针的使用

//通过*操作指针变量指向的内存

cout << "*p = " << *p << endl;

}

void space() {

int a = 10;

int *p;

p = &a; //指针指向数据a的地址

cout << *p << endl; //* 解引用

cout << sizeof(p) << endl;

cout << sizeof(char *) << endl;

cout << sizeof(float *) << endl;

cout << sizeof(double *) << endl;

}

void null_pointer() {

//指针变量p指向内存地址编号为0的空间

int *p = NULL;

//访问空指针报错

//内存编号0 ~255为系统占用内存，不允许用户访问

cout << *p << endl;

}

void wild_pointer() {

//指针变量p指向内存地址编号为0x1100的空间

int *p = (int *) 0x1100;

//访问野指针报错

cout << *p << endl;

}

void const_pointer() {

int a = 10;

int b = 10;

//const修饰的是指针，指针指向可以改，指针指向的值不可以更改

const int *p1 = &a;

int const *pp2 = &a;

p1 = &b; //正确

pp2 = &b; //正确

a = 20;

//*p1 = 100; //报错

//*pp2 = 1;

//const修饰的是常量，指针指向不可以改，指针指向的值可以更改

int *const p2 = &a;

//p2 = &b; //错误

*p2 = 100; //正确

cout << *p2 << endl;

//const既修饰指针又修饰常量

const int *const p3 = &a;

//p3 = &b; //错误

//*p3 = 100; //错误

}

void array() {

int arr[] = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10};

int *p = arr; //指向数组的指针

cout << "第一个元素： " << arr[0] << endl;

cout << "指针访问第一个元素： " << *p << endl;

for (int i = 0; i < 10; i++) {

//利用指针遍历数组

cout << *p << endl;

p++;

}

}

//值传递

void swap1(int a, int b) {

int temp = a;

a = b;

b = temp;

}

//地址传递

void swap2(int *p1, int *p2) {

int temp = *p1;

*p1 = *p2;

*p2 = temp;

}

void function() {

int a = 10;

int b = 20;

swap1(a, b); // 值传递不会改变实参

swap2(&a, &b); //地址传递会改变实参

cout << "a = " << a << endl;

cout << "b = " << b << endl;

}

//冒泡排序函数

void bubbleSort(int *arr, int len) //int * arr 也可以写为int arr[]

{

for (int i = 0; i < len - 1; i++) {

for (int j = 0; j < len - 1 - i; j++) {

if (arr[j] > arr[j + 1]) {

int temp = arr[j];

arr[j] = arr[j + 1];

arr[j + 1] = temp;

}

}

}

}

//打印数组函数

void printArray(int arr[], int len) {

for (int i = 0; i < len; i++) {

cout << arr[i] << endl;

}

}

void sort() {

int arr[10] = {4, 3, 6, 9, 1, 2, 10, 8, 7, 5};

int len = sizeof(arr) / sizeof(int);

bubbleSort(arr, len);

printArray(arr, len);

}

int main(int argc, char *argv[]) {

define();

space();

//null_pointer();

//wild_pointer();

const_pointer();

array();

function();

sort();

return 0;

}