ch2/2-3.c


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#include <stdio.h>


unsigned int htoi(char hex[]) {
    char c;
    int i;
    int length;
    int power;
    unsigned int result;

    for (length = 0; hex[length] != '\0'; ++length)

    power = 1;
    result = 0;

    for (i = length - 1; i >= 0; --i) {
        c = hex[i];
        printf("%c\n", c);

        if (c >= 'a' && c <= 'f')
            c = c - 'a' + 10;
        else if (c >= 'A' && c <= 'F')
            c = c - 'A' + 10;
        else if (c >= '0' && c <= '9')
            c = c - '0';
        else if (c == 'x' || c == 'X')
            break;
        else
            return 0;

        result += c * power;
        power *= 16;
    }

    return result;
}


int main() {
    char hex[] = "0x589";
    printf("%d\n", htoi(hex));
}