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comparison src/collatz.c @ 0:307a81e46071 tip

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author Robert McIntyre <rlm@mit.edu>
date Tue, 18 Oct 2011 01:17:49 -0700
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-1:000000000000 0:307a81e46071
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