Groupon Noodles by Prepare:max Cycle Length

The topic is to encounter even/2, encounter odd number + 1 topics, and then find a range of all the numbers in Max cycle length. For a number, say 44, according to the formula of the problem is calculated, the process is 44, 22, 11, 8, 9, 1 (blind), from 44 to 1 of the length of this sequence, called cycle length. Then the title is given a range, such as [2,300], which asks for the maximum value of the cycle length of all the numbers. Follow up run 1 to 1 million

A number of a number is slowly calculated, the following algorithm to find the cycle length of each number

1  Packagesorting;2 ImportJava.util.*;3 4  Public classSolution2 {5      PublicList<integer> Maxcyclelen (intMinintmax) {6List<integer> maxcycle =NewArraylist<integer>();7          for(intI=min; i<=max; i++) {8 Helper (maxcycle, i);9         }Ten         returnmaxcycle; One     } A      -      Public voidHelper (list<integer> maxcycle,intnum) { -         intLen = 1; the          while(num! = 1) { -             if(num%2 = = 1) num = num*3+1; -             Elsenum = NUM/2; -len++; +         } - Maxcycle.add (len); +     } A  at     /** -      * @paramargs -      */ -      Public Static voidMain (string[] args) { -         //TODO auto-generated Method Stub -Solution2 Sol =NewSolution2 (); inlist<integer> res = Sol.maxcyclelen (1, 100000); - System.out.println (res); to     } +  -}

Follow up: Build a lookup table, count the numbers and don't forget it.

1  Packagesorting;2 ImportJava.util.*;3 4  Public classSolution3 {5Hashmap<integer, integer>map;6      PublicList<integer> Maxcyclelen (intMinintmax) {7List<integer> maxcycle =NewArraylist<integer>();8Map =NewHashmap<integer, integer>();9          for(intI=min; i<=max; i++) {Ten Helper (maxcycle, i); One         } A         returnmaxcycle; -     } -      the      Public voidHelper (list<integer> maxcycle,intnum) { -         intLen = 1; -         intNumcopy =num; -          while(num! = 1) { +             if(Map.containskey (num)) { -Len + = Map.get (num)-1; +                  Break; A             } at             if(num%2 = = 1) num = num*3+1; -             Elsenum = NUM/2; -len++; -         } - Maxcycle.add (len); - map.put (numcopy, Len); in     } -  to     /** +      * @paramargs -      */ the      Public Static voidMain (string[] args) { *         //TODO auto-generated Method Stub $Solution3 Sol =NewSolution3 ();Panax Notoginsenglist<integer> res = Sol.maxcyclelen (1, 100000); - System.out.println (res); the     } +  A}

Or

1      Public voidHelper (list<integer> maxcycle,intnum) {2         intLen = 0;3         intNumcopy =num;4          while(!Map.containskey (num)) {5             if(num = = 1) {6Map.put (1, 1);7Maxcycle.add (1);8                 return;9             }Ten             if(num%2 = = 1) num = num*3+1; One             Elsenum = NUM/2; Alen++; -         } -Len = len +map.get (num); the Maxcycle.add (len); - map.put (numcopy, Len); -}

Groupon Noodles by Prepare:max Cycle Length