查找字符串中字符的第一个索引

Question

I am supposed to loop through the character of arrays that is passed in and look for the first occurrence of char, then return the index of the first occurrence. if char is not found then I return -1. This seems to work for all characters except the character at 0, which it does not find for some reason.

int find_ch_index(char string[], char ch) {
    int i = 0;
    while (string[i++]) {
            if (string[i] == ch) {
                    return i;
            }
    }
    return -1;
}

Answer 1

You should increment i at the end of the while loop:

int find_ch_index(char string[], char ch) {
    int i = 0;
    while (string[i]) {
        if (string[i] == ch) {
            return i;
        }
        i++
    }
    return -1;
}

Answer 2

You won't find the first char ever, because: while (string[i++])

Increments i from '0' to '1', so the statement at 'if' never compares the first char.

Quit this increment and do it at the end of the loop.

Answer 3

我正在while循环中从0增加到1。

Answer 4

In the while condition

while (string[i++]) {

you increased index i. Thus in the next statement

        if (string[i] == ch) {

you are using the increased index.

The function can be written the following way

int find_ch_index( const char string[], char ch ) 
{
    int i = 0;

    while ( string[i] && string[i] != ch ) i++;

    return string[i] == ch ? -1 : i;
}