//
// 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;
}