本文学习自狄泰软件学院 唐佐林老师的 C语言进阶课程，图片全部来源于课程PPT，仅用于个人学习记录

字符串

实验-字符串定义

#include <stdio.h>

int main()
{
    char ca[] = {'H', 'e', 'l', 'l', 'o'};
    char sa[] = {'W', 'o', 'r', 'l', 'd', '\0'};
    char ss[] = "Hello world!";
    char* str = "Hello world!";

    printf("%s\n", ca);
    printf("%s\n", sa);
    printf("%s\n", ss);
    printf("%s\n", str);

    return 0;
}

    /*
    output:
Hello$0@        //缺失\0
World
Hello world!
Hello world!
    */

实验-字符串作为字符数组使用

#include <stdio.h>

int main()
{
    char b = "abc"[0];
    char c = *("123" + 1);
    char t = *"";

    printf("%c\n", b);
    printf("%c\n", c);
    printf("%d\n", t);

    printf("%s\n", "Hello");
    printf("%p\n", "World");

    return 0;
}

    /*
    output:
a
2
0
Hello
00403032
    */

实验-字符串长度判断

#include <stdio.h>
#include <string.h>

int main()
{
    char s[] = "Hello\0world";
    int i = 0;

    for(i=0; i<sizeof(s)/sizeof(char); i++)
    {
        printf("%c\n", s[i]);
    }

    printf("%s\n", s);

    printf( "%d\n", strlen(s) );
    printf( "%d\n", strlen("123") );


    return 0;
}

    /*
    output:
H
e
l
l
o

w
o
r
l
d

Hello
5
3
    */

小结

C语言通过字符数组模拟字符串
C语言中的字符串使用’\0’作为结束符
字符串字面量的本质为字符数组
字符串相关函数都依赖于结束符’\0’

字符串问题分析

实验-snprintf

char buff[10]={'0'};
    char src[] = "hello %s";
    snprintf(buff,sizeof(buff),src);//output:hello ?a    缺失格式化信息
    snprintf(buff,sizeof(buff),src,"wo");//hello wo
    printf("%s\n",buff);

实验-字符数组,strlen,sizeof

    #define STR "Hello, \0D.T.Software\0"

    char* src = STR;
    char buf[255] = {0};

    snprintf(buf, sizeof(buf), src);

    printf("strlen(STR) = %d\n", strlen(STR));//7
    printf("sizeof(STR) = %d\n", sizeof(STR));//21+1=22

    printf("strlen(src) = %d\n", strlen(src));//7
    printf("sizeof(src) = %d\n", sizeof(src));//8 xx  指针的大小 4

    printf("strlen(buf) = %d\n", strlen(buf));//255
    printf("sizeof(buf) = %d\n", sizeof(buf));//255

    printf("src = %s\n", src);//"Hello, "
    printf("buf = %s\n", buf);//"Hello, "
    
//strlen(STR) = 7
//sizeof(STR) = 22
//strlen(src) = 7
//sizeof(src) = 4
//strlen(buf) = 7
//sizeof(buf) = 255
//src = Hello,
//buf = Hello,

实验-字符串相等比较

    #define S1 "D.T.Software"
    #define S2 "D.T.Software"

    if( S1 == S2 )
    {
        printf("Equal\n");
    }
    else
    {
        printf("Non Equal\n");
    }

    if( strcmp(S1, S2) == 0 )
    {
        printf("Equal\n");
    }
    else
    {
        printf("Non Equal\n");
    }
//output:
//Equal
//Equal

实验-循环右移

#include <stdio.h>
#include <string.h>
//目标字符串的指针， 结果字符串指针，移动位数
void right_shift_r(const char* src, char* result, unsigned int n)
{
    const unsigned int LEN = strlen(src);
    int i = 0;

    for(i=0; i < LEN; i++)
    {
        result[(n + i) % LEN] = src[i];
    }

    result[LEN] = '\0';
}

int main()
{
    char result[255] = {0};

    right_shift_r("abcde", result, 2);

    printf("%s\n", result);

    right_shift_r("abcde", result, 5);

    printf("%s\n", result);

    right_shift_r("abcde", result, 8);

    printf("%s\n", result);

    return 0;
}


    /*
    output:
deabc
abcde
cdeab
    */