Exercise 1.4 of cracking coding interview

is_perm_of_pal.c

#include <stdio.h>
#include <stdbool.h>
#include <ctype.h>

#define EXT_ASCII_LEN 256

static bool is_perm_of_pal(const char* restrict s)
{
    if (!s) {
        return false;
    }
    int counts[EXT_ASCII_LEN] = {};
    for (; *s; ++s) {
        if (isalnum(*s)) {
            ++counts[tolower(*s)];
        }
    }
    int oddCnt = 0;
    for (int i = 0; i < EXT_ASCII_LEN; ++i) {
        if (counts[i] > 0 && counts[i] & 1) {
            ++oddCnt;
        }
    }
    return oddCnt < 2;
}

int main(int argc, char** argv)
{
    if (argc < 2) {
        printf("usage: %s <string>\n", argv[0]);
        return 0;
    }
    printf("%d\n", is_perm_of_pal(argv[1]));

    return 0;
}