C语言练习 -- 5

#define _CRT_SECURE_NO_WARNINGS 1

#include<stdio.h>
#include<assert.h>

描述一个学生.一些数据
名字
年龄
电话
性别

struct 结构体关键字  Stu - 结构体标签   struct Stu - 结构体类型

struct Stu
{
    //成员变量
    char name[20];
    short age;
    char tele[12];
    char sex[5];
}s1,s2,s3;//是3个全局的结构体变量


typedef struct Stu
    {
        //成员变量
        char name[20];
        short age;
        char tele[12];
        char sex[5];
    }Stu;//是3个全局的结构体变量

int main()
{
    Stu s1 = {"张三",20,"48355456532","男"};//局部的结构体变量
    Stu s2 = {"旺财",30,"13451521255","保密"};
    return 0;
}


struct S
{
    int a;
    char c;
    char arr[20];
    double d;
};

struct T
{
    char ch[10];
    struct S s;
    char* pc;
};

int main()
{
    char arr[] = "hello bit\n";
    struct T t = { "hehe",{1,'w',"hello world",3.14},arr};
    printf("%s\n", t.ch);//hehe
    printf("%s\n", t.s.arr);//hello world
    printf("%lf\n", t.s.d);//3.14
    printf("%s\n", t.pc);//hello bit
    return 0;
}


typedef struct Stu
    {
        char name[20];
        short age;
        char tele[12];
        char sex[5];
    }Stu;

void print1(Stu tmp)
{
    printf("name: %s\n", tmp.name);
    printf("age: %d\n", tmp.age);
    printf("tele: %s\n", tmp.tele);
    printf("sex: %s\n", tmp.sex);
}

void print2(Stu* s)
{
    printf("name: %s\n", s->name);
    printf("age: %d\n", s->age);
    printf("tele: %s\n", s->tele);
    printf("sex: %s\n", s->sex);
}

int main()
{
    Stu s = { "李四",40,"11544845315","男" };
    //打印结构体数据
    //print1和print2 哪个更好？
    //print2更优
    print1(s);
    print2(&s);
    return 0;
}

Add(int a, int b)
{
    int z = 0;
    z = a + b;
    return z;
}

int main()
{
    int a = 20;
    int b = 10;
    int ret = 0;
    ret = Add(a, b);
    printf("%d\n", ret);
    return 0;
}

栈：先进后出，后进先出
插入一个元素：压栈
删除一个元素：出栈


int main()
{
    int i = 0;
    for (i = 0; i < 100; i++)
    {
        printf("%d ", i);
    }
    return 0;
}

Debug 调试版本
Release 发布版本

F5 - 启动调试 - 和F9配合使用

断点 F9切换断点

int main()
{
    int i = 0;
    int arr[10] = { 1,2,3,4,5,6,7,8,9,10 };
    for (i = 0; i <= 12; i++)
    {
        printf("hehe\n");
        arr[i] = 0;
    }
    return 0;
}


int main()
{
    int i = 0;
    for (i = 0; i < 100; i++)
    {
        printf("%d ", i);
    }

    for (i = 0; i < 100; i++)
    {
        printf("%d ",10-i);
    }

    return 0;
}

int Add(int x, int y)
{
    return x + y;
}

int main()
{
    printf("hehe\n");
    int a = 10;
    int b = 10;
    int c = Add(a, b);
    return 0;
}


int main()
{
    {
        int tmp = 0;
        printf("tmp = %d\n", tmp);
    }
    int arr[10] = { 0 };
    int i = 0;
    for (i = 0; i < 10; i++)
    {
        arr[i] = i;
    }
    return 0;
}

void test2()
{
    printf("hehe\n");
}

void test1()
{
    test2();
}
void test()
{
    test1();
}

int main()
{
    test();
    return 0;
}

void my_strcpy(char* dest,char* src)
{
    if (dest != NULL && src != NULL)
    {
        while (*dest++ = *src++)
        {
            ;//优化
            //*dest = *src;
            //src++;
            //dest++;
        }
        *dest = *src;
    }
}

好代码
char* my_strcpy(char* dest, const char* src)
{
    char* ret = dest;
    assert(dest != NULL);//断言
    assert(src != NULL);//断言
    //把src指向的字符串拷贝到dest指向的空间，包含‘\0’字符
    while (*dest++ = *src++)
        {
            ;//优化
            //*dest = *src;
            //src++;
            //dest++;
        }
    return ret;
}

int main()
{
    //strcpy
    //字符串拷贝
    char arr1[] = "###";
    char arr2[] = "bit";

    printf("%s\n", my_strcpy(arr1, arr2));
    return 0;
 }


int main()
{
    const int num = 10;

    const int* p = &num;
    //*p = 20;
    //error const 放在指针变量的*左边时，修饰的是*p，也就是说：不能通过p来改变*p（num）的值
    //const 放在指针变量的*右边时，修饰的是指针变量p本身，p不能被改变
    int n = 100;
    p = &n;
    printf("%d\n", num);
    return 0;
}

int my_strlen(const char* str)
{
    int count = 0;
    assert(str != NULL);//断言指针 - 保证指针的有效性
    while (*str != '\0')
    {
        count++;
        str++;
    }
    return count;
}

int main()
{
    char arr[] = "abcdef";
    int len = my_strlen(arr);
    printf("%d\n", len);
    return 0;
}