/home/toolbox/public_html/solutions/1/100/i.c
1 /* @JUDGE_ID: 823125 100 C "The 3n+1 problem uses recursive function for cycle computation"*/
2 /**************
3 Solution to Problem 100
4 by: Theodore A. Irra
5 date: 02/04/2016
6 **************/
7 #include <stdio.h>
8 long process_number(long ); /* see implementation after main */
9 long cycle; /* potentially perilous global variable but program is short */
10 int main()
11 {
12 long i,j, /* input integers */
13 num, /* number of integers in the cycle in the range i, j being processed */
14 low, /* global variable used to determine maximum cycle length */
15 high, /* as above */
16 cycle, /* current cycle length so far, initialized to 0 */
17 cycle_max = 0; /* initial maximum cycle length, initialized to 0 */
18 while (scanf("%d %d",&i,&j) != EOF)
19 {
20 cycle = 0; /* initialize for each integer set */
21 if (i < j) /* input must be in ascending order */
22 {
23 low = i;
24 high = j;
25 }
26 else
27 {
28 low = j;
29 high = i;
30 }
31 num = low; /* begin with lowest */
32 cycle_max = cycle; /* initialize */
33 while (num <= high)
34 {
35 cycle = process_number(num); /* function call */
36 if (cycle > cycle_max) cycle_max = cycle; /* update result-so-far */
37 num++; /* advance one */
38 }
39 printf("%d %d %d\n",i,j,cycle_max);
40 } /* end while */
41 return (0);
42 } /* end main */
43 long process_number( long n)
44 /* recursive function that computes the cycle length of integer passed in using the given algorithm*/
45 {
46 cycle = 1; /* initialize each time */
47 if (n == 1) return 1; /* base case */
48 else
49 {
50 if ((n % 2) != 0 ) process_number(( 3*n ) + 1); /* conditioinal recursive call*/
51 else process_number( n/2 ); /* conditional recursive call*/
52 cycle++; /* update cycle length*/
53 }
54 return cycle;
55 }
56