I want to know why this result is output - c

Question

source code
/***************************************************
* Copyright: 2023, 黄子涵.
* File name: huangzihan_c_program_142
* Description: 改变指针的值
* Author: 黄子涵
* Version: V1.0.0
* Date: 2023-01-08
* ****************************************************/
#include <stdio.h>
char huangzihan[10];
char huangchunqin[12];
char chenlanying[12];
char shejiazi[8];
void name_input();
void name_output();
void name_output_n();
void name_input()
{
int i;
printf("*********************************\n");
printf(" 给字符数组输入对应的名字 \n");
printf("*********************************\n");
printf("请输入黄子涵的小写拼音：");
for (i = 0; i < 10; i++)
{
scanf("%c", &huangzihan[i]);
if (huangzihan[i] == 10)
{
huangzihan[i] = '\0';
break;
}
}
getchar();
printf("请输入黄春钦的小写拼音：");
for (i = 0; i < 12; i++)
{
scanf("%c", &huangchunqin[i]);
if (huangchunqin[i] == 10)
{
huangchunqin[i] = '\0';
break;
}
}
getchar();
printf("请输入陈兰英的小写拼音：");
for (i = 0; i < 11; i++)
{
scanf("%c", &chenlanying[i]);
if (chenlanying[i] == 10)
{
chenlanying[i] = '\0';
break;
}
}
getchar();
printf("请输入佘佳梓的小写拼音：");
for (i = 0; i < 8; i++)
{
scanf("%c", &shejiazi[i]);
if (shejiazi[i] == 10)
{
shejiazi[i] = '\0';
break;
}
}
printf("\n");
}
void name_output()
{
char *p1,*p2,*p3,*p4;
printf("*********************************\n");
printf(" 将字符数组对应的名字输出 \n");
printf("*********************************\n");
printf("输出huangzihan：");
p1 = huangzihan;
printf("%s", p1);
printf("\n");
printf("输出huangchunqin：");
p2 = huangchunqin;
printf("%s", p2);
printf("\n");
printf("输出chenlanying：");
p3 = chenlanying;
printf("%s", p3);
printf("\n");
printf("输出shejiazi：");
p4 = shejiazi;
printf("%s", p4);
printf("\n");
}
void name_output_n()
{
int i;
char *p;
printf("\n");
printf("*********************************\n");
printf(" 改变指针的值 \n");
printf("*********************************\n");
printf("你要从第几个字符输出huangzihan（共10个字符）？");
scanf("%d", &i);
p = huangzihan + i - 1;
printf("这是你要输出的字符串：%s", p);
printf("\n");
printf("你要从第几个字符输出huangchunqin（共12个字符）？");
scanf("%d", &i);
p = huangchunqin + i - 1;
printf("这是你要输出的字符串：%s", p);
printf("\n");
printf("你要从第几个输出chenlanying（共11个字符）？");
scanf("%d", &i);
p = chenlanying + i - 1;
printf("这是你要输出的字符串：%s", p);
printf("\n");
printf("你要从第几个输出shejiazi（共8个字符）？");
scanf("%d", &i);
p = shejiazi + i - 1;
printf("这是你要输出的字符串：%s", p);
printf("\n");
}
int main()
{
extern char huangzihan[10];
extern char huangchunqin[12];
extern char chenlanying[12];
extern char shejiazi[8];
name_input();
name_output();
name_output_n();
return 0;
}
At first, I thought it was the problem of not adding the end tag of the string, but I added the end tag of the string and found it didn't work.Add code as follows：
if (shejiazi[i] == 10) {
shejiazi[i] = '\0';
break;
}
I want to output results
输出huangzihan：huangzihan
输出huangchunqin：huangchunqin
输出chenlanying：chenlanying
输出shejiazi：shejiazi
Actual output results
I want to know why this happens. If you know, please tell me. Thank you very much。

Answer 1

If the input string has exactly the maximum number of characters, the target array is not null terminated, causing printf("...%s", ...) to have undefined behavior. If your case it seems the arrays huangchunqin and chenlanying are adjacent in memory, so printf("%s",p2); outputs the contents of huangchunqin until it finds a null terminator, which does not occur before the end of chenlanying.
You should make the arrays one byte longer and use a function to read these strings:
/* Author: 查理戈登 */
/* Description: 程序的修改版本 */
#include <stdio.h>
char huangzihan[11];
char huangchunqin[13];
char chenlanying[13];
char shejiazi[9];
// read a string into a char array of a given length,
// return EOF if no input at end of file, 1 if truncated, 0 otherwise
int input_string(const char *prompt, char *dest, size_t size) {
size_t i = 0;
int c;
int result = 0;
printf("%s: ", prompt);
while ((c = getchar()) != EOF && c != '\n') {
if (i + 1 < size) {
dest[i++] = c;
} else {
result = 1;
}
}
dest[i] = '\0';
if (i == 0 && c == EOF)
result = EOF;
return result;
}
void name_input(void) {
printf("*********************************\n");
printf(" 给字符数组输入对应的名字 \n");
printf("*********************************\n");
// Qǐng shūrù shéjiāzǐ de xiǎoxiě pīnyīn
input_string("请输入黄子涵的小写拼音", huangzihan, sizeof huangzihan);
input_string("请输入黄春钦的小写拼音", huangchunqin, sizeof huangchunqin);
input_string("请输入陈兰英的小写拼音", chenlanying, sizeof chenlanying);
input_string("请输入佘佳梓的小写拼音", shejiazi, sizeof shejiazi);
printf("\n");
}

Answer 2

In name_input() you don't terminate your strings correctly as the last iteration is i=9:
for(i=0;i<10;i++) {
scanf("%c",&huangzihan[i]);
if(huangzihan[i]==10)
{
huangzihan[i]='\0';
break;
}
}
Instead you could do:
int i = 0;
for(; i < sizeof huangzihan - 1; i++) {
scanf("%c", &huangzihan[i]);
}
huangzihan[i] = '\0';
I don't know if your letters entered fit into the char if not you will get some weird corruption.
You can also just read a string with:
#define huangzihan_len 9
#define str(s) str2(s)
#define str2(s) #s
char huangzihan[huangzihan_len+1];
//...
scanf("%" str(huangzihan_len) "s", huangzihan);
After reading a string you do getchar() presumably to get rid of the newline. You can change the format string with an initial space to do that automatically " %c", or make a flush function that discards all data till you hit a new line:
void flush() {
for(;;) {
int ch = getchar();
if(ch == EOF || ch == '\n') return;
}
}
Your code is repetitive so consider using an array to hold your strings, as they are different length perhaps an array of string pointers char *str[4]?