/*
  Pi Spigot from April '95 Math Monthly
                  ----------------------

  The program basically evaluates n terms of a series for pi
  by starting with the last term and multiplying by 10 and carrying the
  remainder to the next term, reading off the ones digit, and repeating
  until all numerators are zeroed.
  Check out the issue for a more detailed explanation.

  Improved output by Robert Simms, of Salsibury, MD

  Language: C (manually converted from Pascal)
*/

#include <stdlib.h>
#include <stdio.h>

digitout(int count, int digit)
{
    printf("%d", digit);
    if (count%5==0)
        printf(" ");
    if (count%20==0)
        printf("\n");
    if (count%100==0)
       printf("\n");
}

int main(int argc, char *argv[])
{
    register int count, i, j, k, len, n, nines, predigit, q, x;
    int *a;

    count=-2;
    predigit=0;
    nines=0;
    if (--argc)
        n=atoi(argv[1])+2;
    else {
        fprintf(stderr,
            "Digits of pi -- usage: %s integer\n returns the requested number of decimal digits of pi, give or take one\n", argv[0]);
    return 1;
    }

    len=10*n/3;
    a=(int *) malloc(len * sizeof(int));
    for(j=0; j<len; j++)
        *(a+j)=2;
    for (j=0; j<n; j++) {
        q=0;
        for (i=len-1; i>=0; i--) {
            x=10**(a+i)+q*(i+1);
            *(a+i)=x%(2*i+1);
            q=x/(2*i+1);
        }
        *a=q%10;
        q=q/10;
        switch(q) {
        case 10:
            digitout(++count, predigit +1);
            for(k=0; k<nines; k++)
                digitout(++count, 0);
            predigit=0; nines=0;
            break;
        case  9:
            nines++;
            break;
        default:
            digitout(++count, predigit);
            predigit=q;
            if(nines!=0) {
                for(k=0; k<nines; k++)
                    digitout(++count, 9);
                nines=0;
            }
            break;
        }
    }
    if (count%20!=0)
        printf("\n");
    return 0;
}