Look and Say

/* Look and say sequence calculator by Braden Best
 * Inspired by a numberphile video: https://www.youtube.com/watch?v=ea7lJkEhytA
 */
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#define BUFSZ 100000

void
build(char *buf)
{
    char buf2[BUFSZ] = "",
         *buf2_p = buf2,
         temp;
    int digit,
        count;

    strncpy(buf2, buf, strlen(buf));

    while(*buf2_p){
        temp = *buf2_p;
        count = 0;

        while(*buf2_p && *buf2_p == temp){
            buf2_p++;
            count++;
        }

        digit = temp - '0';
        snprintf(buf, 3, "%i%i", count, digit);
        buf += 2;
    }
}

void
look_and_say(int n, int lim)
{
    char buf[BUFSZ] = "";
    int i;

    printf("Seed: %i\n\n", n);
    snprintf(buf, BUFSZ, "%i", n);

    for(i = 1; i <= lim; i++){
        build(buf);
        printf("Generation %i: %s\n\n", i, buf);
    }
}

int
main(int argc, char **argv)
{
    if(argv[1] && argv[2]){
        look_and_say(atoi(argv[1]), atoi(argv[2]));
    } else {
        printf( "Usage: %s [starting point] [number of generations]\n"
                "Try %s 1 7\n",
                argv[0],
                argv[0]);
    }
}