Recursive algorithm and optimization

1  Packageinterview;2 //There is a Fibonacci sequence function, the first k number is 1, and no one behind is the sum of the former K-bit, for example, k=4, the function3 //The function returns a value of 1,1,1,1,4,7,13,25,494  Public classRecursiveoptimize {5     Static intFib_k (intNintk) {6          if(n<k)7             return1;8          intresult = 0;9           for(inti=0;i<k;i++){TenResult + = Fib_k (n-i-1, k); One          } A          returnresult; -     } -     Static intFib_k_optimize (intNintk) { the         if(n<k) -             return1; -         int[] fib =New int[N+1]; -          for(inti=0;i<k;i++){ +Fib[i]=1; -         } +          for(inti=k;i<=n;i++) { A             intresult = 0; at              for(intj=0;j<k;j++){ -Result + = Fib[i-j-1]; -             } -fib[i]=result; -         } -         returnFib[n]; in     } -      Public Static voidMain (string[] args) { to         LongStart =system.nanotime (); +          for(inti=0;i<20;i++){ -System.out.print (Fib_k (i,4) + ""); the         } *         LongEnd =system.nanotime (); $System.out.println ("\ n" + (end-start));Panax Notoginseng          -         //=================================== theStart =system.nanotime (); +          for(inti=0;i<20;i++){ ASystem.out.print (Fib_k_optimize (i,4) + ""); the         } +End =system.nanotime (); -System.out.println ("\ n" + (end-start)); $     } $      -}

Recursive algorithm and optimization