hash.c

#include <stdio.h>
#include <string.h>

unsigned int hash(char *k) {
    unsigned int result = 0;
    size_t len = strlen(k);
    if (len == 0) {
        return 0;
    } else if (len == 1) {
        return k[0];
    }
    for (unsigned int i = 0; i < len - 1; i++) {
        result <<= 1;
        result += k[i+1] * (k[i] - 1);
    }
    return result;
}

int main(int argc, char **argv) {
    if (argc < 2) {
        const int SIZE = 1024;
        char buf[SIZE];
        while(fgets(buf, SIZE, stdin) != NULL) {
            size_t pos = strlen(buf) - 1;
            if (buf[pos] == '\n') {
                buf[pos] = 0;
            }
            printf("%u\n", hash(buf));
        }
        return 0;
    }
    printf("%u\n", hash(argv[1]));
    return 0;
}