如何编写一个 C 语言程序来查找字符串中字符的首次出现，并附带示例？
C 语言查找字符串中字符首次出现位置的程序 示例 1
此程序允许用户输入一个字符串（或字符数组）和一个字符值。接下来，它将使用 If Else 语句搜索并查找字符在字符串中的首次出现。
/* C Program to find First Occurrence of a Character in a String */
#include <stdio.h>
#include <string.h>
int main()
{
char str[100], ch;
int i, Flag;
Flag = 0;
printf("\n Please Enter any String : ");
gets(str);
printf("\n Please Enter the Character that you want to Search for : ");
scanf("%c", &ch);
for(i = 0; i <= strlen(str); i++)
{
if(str[i] == ch)
{
Flag++;
break;
}
}
if(Flag == 0)
{
printf("\n Sorry!! We haven't found the Search Character '%c' ", ch);
}
else
{
printf("\n The First Occurrence of the Search Element '%c' is at Position %d ", ch, i + 1);
}
return 0;
}
首先，我们使用 For 循环 遍历字符串中的每个字符。
for(i = 0; i <= strlen(str); i++)
{
if(str[i] == ch)
{
Flag++;
break;
}
}
str[] = Hello World
ch = l
Flag = 0
首次迭代循环：for(i = 0; i <= strlen(str); i++)
在 For 循环内，我们使用 If 语句 来检查 str[0] 是否等于用户指定的字符。
if(str[i] == ch) => if(H == l)
上述条件为假。因此，i 将递增，Flag 仍然为 0。
第二次迭代：for(i = 1; 1 <= 11; 1++)
if(str[i] == ch) => if(e == l) – 条件为假。因此，i 值将递增，Flag 仍然为 0。
第三次迭代：for(i = 2; 2 <= 11; 2++)
if(str[i] == ch) => if(l == l)
上述条件为真。
Flag++ 表示 Flag = 1，并且 break 语句 将退出循环。
接下来，我们使用 If Else 语句 来检查 Flag 值是否等于 0。这里，条件为假。因此，else 块中的语句将被执行。
printf("\n The First Occurrence of the Search Element '%c' is at Position %d ", ch, i + 1);
这里，i 是索引位置（从零开始），i + 1 是实际位置。
C 语言查找字符串中字符首次出现位置的程序 示例 2
此程序与上述程序相同。这里，我们只是将 C 语言 For 循环 替换为 While 循环。
/* C Program to find First Occurrence of a Character in a String */
#include <stdio.h>
#include <string.h>
int main()
{
char str[100], ch;
int i, Flag;
i = Flag = 0;
printf("\n Please Enter any String : ");
gets(str);
printf("\n Please Enter the Character that you want to Search for : ");
scanf("%c", &ch);
while(str[i] != '\0')
{
if(str[i] == ch)
{
Flag++;
break;
}
i++;
}
if(Flag == 0)
{
printf("\n Sorry!! We haven't found the Search Character '%c' ", ch);
}
else
{
printf("\n The First Occurence of the Search Element '%c' is at Position %d ", ch, i + 1);
}
return 0;
}
Please Enter any String : tutorial gateway
Please Enter the Character that you want to Search for : a
The First Occurence of the Search Element 'a' is at Position 7C 语言查找字符串中字符首次出现位置的程序 示例 3
这个关于字符首次出现的 C 程序与第一个示例相同。这次，我们使用了 函数 的概念来分离逻辑。
/* C Program to find First Occurrence of a Character in a String */
#include <stdio.h>
#include <string.h>
int Find_FirstCharcater(char str[], char ch);
int main()
{
char str[100], ch;
int index;
printf("\n Please Enter any String : ");
gets(str);
printf("\n Please Enter the Character that you want to Search for : ");
scanf("%c", &ch);
index = Find_FirstCharcater(str, ch);
if(index == -1)
{
printf("\n Sorry!! We haven't found the Search Character '%c' ", ch);
}
else
{
printf("\n The First Occurrence of the Search Element '%c' is at Position %d ", ch, index + 1);
}
return 0;
}
int Find_FirstCharcater(char str[], char ch)
{
int i;
for(i = 0; str[i] != '\0'; i++)
{
if(str[i] == ch)
{
return i;
}
}
return -1;
}
Please Enter any String : learn c programming
Please Enter the Character that you want to Search for : m
The First Occurrence of the Search Element 'm' is at Position 15查找字符串中字符首次出现位置的程序 示例 4
这个 查找字符首次出现 的程序与第一个示例相同。但是，这次我们使用了 指针 的概念。
/* C Program to find First Occurrence of a Character in a String */
#include <stdio.h>
#include <string.h>
int Find_FirstCharcater(char *str, char ch);
int main()
{
char str[100], ch;
int index;
printf("\n Please Enter any String : ");
gets(str);
printf("\n Please Enter the Character that you want to Search for : ");
scanf("%c", &ch);
index = Find_FirstCharcater(str, ch);
if(index == -1)
{
printf("\n Sorry!! We haven't found the Search Character '%c' ", ch);
}
else
{
printf("\n The First Occurrence of the Search Element '%c' is at Position %d ", ch, index + 1);
}
return 0;
}
int Find_FirstCharcater(char *str, char ch)
{
int i;
while(*str)
{
if(*str == ch)
{
return i;
}
i++;
str++;
}
return -1;
}
Please Enter any String : programming examples
Please Enter the Character that you want to Search for : a
The First Occurrence of the Search Element 'a' is at Position 6