Whether the Java programmer should know a bit about the algorithm (a simple recursive calculation of the Fibonacci sequence of the case illustrates the importance of the algorithm to the program)

Tagged with: Fibonacci memo recursive one Fibonacci demo RIP cache start

Why say " algorithm is the soul of the program is not too much", please see the following simple case

1  Packagerecursion;2 3 ImportJava.util.HashMap;4 ImportJava.util.Map;5 6 Importorg.junit.Test;7 8 /**      9  * @author: MengxianmanTen * @creationTime: November 27, 2017 morning 9:47:51 One * @description: The simple use of the Fibonacci sequence combination memo algorithm A  */ -  Public classMemorandumdemo { -     //calculation method Execution times the     Private Longcount; -     //The map collection is used as a memo to hold the calculated value of Fibo (n) -     PrivateMap<integer, long> map =NewHashmap<>(); -      +     //method One: Do not use the Map collection as the memo cache data -      Public LongFibo (Integer N) { +count++; A         if(n = = 1 | | n = = 2){ at             return1; -}Else{     -             returnFibo (n-1) + Fibo (n-2); -         } -     } -     //method Two: Use the Map collection as a memo to cache data in      Public LongFibo2 (Integer N) { -count++; to         if(n = = 1 | | n = = 2){ +             return1; -}Else{     the             if(!Map.containskey (n)) { *Map.put (n, Fibo2 (n-1) + Fibo2 (n-2)); $             }Panax Notoginseng             returnmap.get (n); -         } the     } +      A @Test the      Public voidtest1 () { +         LongStart =System.currenttimemillis (); -         Longresult = Fibo (50); $         LongEnd =System.currenttimemillis (); $SYSTEM.OUT.PRINTLN ("Calculated result:" +result); -SYSTEM.OUT.PRINTLN ("Time Consuming:" + (End-start) + "millisecond"); -System.out.println ("Method execution Count:" +count); the         /*Test Results - * Calculation result: 12586269025Wuyi * Time consuming: 77318 Ms the * Method Execution times: 25172538049 -         */ Wu     } -      About @Test $      Public voidtest2 () { -         LongStart =System.currenttimemillis (); -         Longresult = Fibo2 (50); -         LongEnd =System.currenttimemillis (); ASYSTEM.OUT.PRINTLN ("Calculated result:" +result); +SYSTEM.OUT.PRINTLN ("Time Consuming:" + (End-start) + "millisecond"); theSystem.out.println ("Method execution Count:" +count); -         /*Test Results $ * Calculation result: 12586269025 the * Time consuming: 0 Ms the * Method Execution times: the         */ the     } -}

Whether the Java programmer should know a bit about the algorithm (a simple recursive calculation of the Fibonacci sequence of the case illustrates the importance of the algorithm to the program)