Найти последнюю цифру a^b

printf("%d", (int)pow((double)(a % 10), (double)b)) % 10);

#include <stdio.h>
#include <stdlib.h>
#include <limits.h>
 
int get_unsigned(const char*, size_t*);
size_t my_pow(size_t, size_t);
 
int main(int argc, char* argv[])
{
    size_t base, exp, result;
    
    if(argc != 3)
    fprintf(stderr, "Usage: %s BASE EXP\n", *argv), exit(1);
    
    if(!get_unsigned(argv[1], &base))
    fprintf(stderr, "%s is not a legal unsigned integer\n", argv[1]), exit(1);
 
    if(!get_unsigned(argv[2], &exp))
    fprintf(stderr, "%s is not a legal unsigned integer\n", argv[2]), exit(1);
 
    result = my_pow(base, exp);
    
    printf("Last digit of %u ^ %u is %u\n", base, exp, result);
    
    exit(0);
}
 
int get_unsigned(const char* buf, size_t* result)
{
    static char* endptr;
    long int temp;
 
    temp = strtol(buf, &endptr, 10);
 
    if(temp == LONG_MIN || temp == LONG_MAX || !(*buf != '\0' && *endptr == '\0') || temp < 0)
    {
    *result =0;
    return 0;
    }
 
    *result = (size_t) temp;
 
    return 1;
}
 
size_t my_pow(size_t base, size_t exp)
{
    size_t result = 1;
 
    base %= 10;
            
    while(exp--)
    {
    result *= base;
    result %= 10;
    }
 
    return result;
}

#include <stdio.h>
#include <stdlib.h>
#include <limits.h>
 
int get_unsigned(const char*, size_t*);
size_t my_pow(size_t, size_t);
 
int main(int argc, char* argv[])
{
    size_t base, exp, result;
    
    if(argc != 3)
    fprintf(stderr, "Usage: %s BASE EXP\n", *argv), exit(1);
    
    if(!get_unsigned(argv[1], &base))
    fprintf(stderr, "%s is not a legal unsigned integer\n", argv[1]), exit(1);
 
    if(!get_unsigned(argv[2], &exp))
    fprintf(stderr, "%s is not a legal unsigned integer\n", argv[2]), exit(1);
 
    result = my_pow(base % 10, exp);
    
    printf("Last digit of %u ^ %u is %u\n", base, exp, result);
    
    exit(0);
}
 
int get_unsigned(const char* buf, size_t* result)
{
    static char* endptr;
    long int temp;
 
    temp = strtol(buf, &endptr, 10);
 
    if(temp == LONG_MIN || temp == LONG_MAX || !(*buf != '\0' && *endptr == '\0') || temp < 0)
    {
    *result =0;
    return 0;
    }
 
    *result = (size_t) temp;
 
    return 1;
}
 
size_t my_pow(size_t base, size_t exp)
{
    size_t temp;
 
    if(exp == 0)
    return 1;
        
    if(exp & 1)
    return (my_pow(base, exp - 1) * base) % 10;
    
    temp = my_pow(base, exp / 2);
    return (temp * temp) % 10;
}