c中是否有一个函数会返回char数组中的索引?

Is there a function in c that will return the index of a char in a char array?

c中是否有一个函数会返回char数组中的索引?

For example something like:

例如像:

char values[] = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ";
char find = 'E';

int index = findInedexOf( values, find );

6 个解决方案

#1

strchr returns the pointer to the first occurrence, so to find the index, just take the offset with the starting pointer. For example:

strchr返回指向第一个事件的指针，因此要找到索引，只需使用起始指针的偏移量。例如:

char values[] = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ";
char find = 'E';

const char *ptr = strchr(values, find);
if(ptr) {
   int index = ptr - values;
   // do something
}

#2

int index = strchr(values,find)-values;

Note, that if there's no find found, then strchr returns NULL, so index will be negative.

注意，如果没有找到，则strchr返回NULL，因此索引将为负。

#3

Safe index_of() function that works even when it finds nothing (returns -1 in such case).

安全的index_of()函数，即使它没有发现任何东西(在这种情况下返回-1)，它仍然有效。

#include <stddef.h>
#include <string.h>
ptrdiff_t index_of(const char *string, char search) {
    const char *moved_string = strchr(string, search);
    /* If not null, return the difference. */
    if (moved_string) {
        return moved_string - string;
    }
    /* Character not found. */
    return -1;
}

#4

What about strpos?

大小写敏感呢?

#include <string.h>

int index;
...
index = strpos(values, find);

Note that strpos expects a zero-terminated string, which means you should add a '\0' at the end. If you can't do that, you're left with a manual loop and search.

注意，strpos希望得到一个零终止的字符串，这意味着您应该在末尾添加一个'\0'。如果你做不到这一点，你就只能进行手动循环和搜索。

#5

There's also size_t strcspn(const char *str, const char *set); it returns the index of the first occurence of the character in s that is included in set:

还有size_t strcspn(const char *str, const char *set);它返回集合中包含的s中第一次出现字符的索引:

size_t index = strcspn(values, "E");

#6

You can use strchr to get a pointer to the first occurrence and the subtract that (if not null) from the original char* to get the position.

您可以使用strchr获取指向第一个事件的指针，并从原始char*中减去该事件(如果不是null)以获取位置。