Mercurial > coderloop

     1 

     2 #include <stdio.h>

     3 #include <stdlib.h>

     4 

     5 int main(int argc, char *argv[]){

     6   FILE *fp;

     7   int n;

     8   if((fp=fopen(argv[1] ,"r")) == NULL) {

     9     printf("Cannot open file.\n");

    10     exit(1);}

    11   fscanf(fp, "%d", &n); /* read from file */

    12   int answer = search_collatz(n);

    13   printf("%d\n", answer); }

    14 

    15 long long collatz_next(long long n){

    16   if (!(n % 2)){

    17     return n/2;}

    18   else {

    19     return 1+(n*3);}}

    20 

    21 int collatz_length(int n){

    22   long long t = n;

    23   int d = 1;

    24   while (t > 1){

    25     t = collatz_next(t);

    26     d++;}

    27   return d;}

    28   

    29 int search_collatz(int n){

    30   int max = 0;

    31   int max_val = 0;

    32   int temp_val;

    33   int i;

    34   for (i = 1; i<n; i++){

    35     temp_val = collatz_length(i);

    36     if (temp_val > max_val){

    37       max = i;

    38       max_val = temp_val;}}

    39   return max;}

    40
author	Robert McIntyre <rlm@mit.edu>
date	Tue, 18 Oct 2011 01:17:49 -0700
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