指针的简单使用

练习题目

封装函数MyStrlen实现获得字符串长度的功能

封装函数MyStrcpy实现字符串拷贝的功能

封装函数MyStrcat实现字符串拼接的功能

封装函数MyStrcmp实现字符串比较的功能

#include<stdio.h>

int MyStrlen(char *pstr)
{
    int n = 0;

    while(*pstr != '\0')
    {
        pstr++;
        n++;
    }

    return n;
}

int MyStrcpy(char *pstr, char *pdst)
{
    while(*pdst != '\0')
    {
        *pstr = *pdst;
        pstr++;
        pdst++;
    }

    return 0;
}

int MyStrcat(char *pstr, char *pdst)
{
    while(*pstr != '\0')
    {
        pstr++;
    }
    
    while(*pdst != '\0')
    {
        *pstr = *pdst;
        pdst++;
        pstr++;
    }

    *pstr = '\0';

    return 0;
}

int MyStrcmp(char *pstr, char *pdst)
{
    while(*pstr != '\0' && *pdst != '\0')
    {
        if(*pstr == *pdst)
        {
            pstr++;
            pdst++;
        }
        else
        {
            break;
        }
    }
    return *pstr - *pdst;
}

int main(void)

{
    char str[32] = {0};
    char dst[32] = {0};
    char a[32] = {0};
    int b = 0;  
    int len = 0;

    gets(str);
    gets(dst);

    len = MyStrlen(str);
    MyStrcpy(a, dst);
    MyStrcat(str, dst);
    b = MyStrcmp(str, dst);

    printf("len = %d\n", len);
    printf("dst拷贝到a = %s\n", a);
    printf("dst拼接str后 = %s\n", str);
    printf("此时str和dst分别是：%s ------%s\n", str, dst);
    printf("str和dst比较后 = %d\n", b);

    return 0;
}

题目二

封装函数实现传入一个字符串，实现字符串的倒置

#include<stdio.h>

//获取字符串长度
int MyStrlen(char *pstr)
{
    int n = 0;

    while(*pstr != '\0')
    {
        pstr++;
        n++;
    }
    return n;
}

//对字符串进行倒置
int Strlnvert(char *pstr, char *pdst, int len)
{
    while(*pstr != '\0')
    {
        *(pdst+len-1) = *pstr;
        pstr++;
        pdst--;
    }

    return 0;
}

//主函数
int main(void)

{
    char str[32] = {0};
    char dst[32] = {0};

    gets(str);
    
    Strlnvert(str, dst, MyStrlen(str));

    printf("倒置后= %s\n", dst);

    return 0;
}