#include <stdio.h>
const unsigned long fast_atoi_map [] = {
0, 10, 20, 30, 40, 50, 60, 70, 80, 90,
0, 100, 200, 300, 400, 500, 600, 700, 800, 900,
0, 1000, 2000, 3000, 4000, 5000, 6000, 7000, 8000, 9000,
0, 10000, 20000, 30000, 40000, 50000, 60000, 70000, 80000, 90000,
0, 100000, 200000, 300000, 400000, 500000, 600000, 700000, 800000, 900000,
};
unsigned long fast_atoi(char *str, unsigned char length) {
unsigned long val = 0;
const unsigned long *imap = fast_atoi_map + (length - 2) * 10;
while (length-- > 1) {
val = val + *(imap + (*str++ - '0'));
imap -= 10;
}
return val + (*str - '0');
}
int main()
{
printf("x=%lu", fast_atoi("0", 1));
return 0;
}
