Fibonacci Issues (Java)

F (n) =f (n-1) +f (n-2)

1. Iterative implementation, O (2 of the n-th square)

1 /**2 * Fibonacci Iterative implementations3      * @paramN4      * @return5      */6      Public intFabonacci_1 (intN) {7         if(n<0)return0;8         if(n==1| | n==2)return1;9         returnFabonacci_1 (n-1) +fabonacci_1 (n-2);Ten}

2. Recursive implementation, O (N)

1 /**2 * Fibonacci Recursive implementations3      * @paramN4      * @return5      */6      Public intFabonacci_2 (intN) {7         if(n<0)return0;8         if(n==1| | n==2)return1;9         intres = 1,pre=1,temp=0;Ten          for(inti=3;i<=n;i++){ Onetemp =Res; Ares = res+Pre; -Pre =temp; -         } the         returnRes; -}

3. Using the second-order matrix implementation, O (LOGN)

1 /**2 * Fibonacci Ponachi Matrix Implementation3      * @paramN4      * @return5      */6      Public intFabonacci_3 (intN) {7         if(n<0)return0;8         if(n==1| | n==2)return1;9         int[] base={{1,1},{1,0}};Ten         int[] res = Matrixpower (base, n-2); One         returnRes[0][0]+res[1][0]; A     } -      -     //using a second-order matrix to find the Fibonacci the      -      Public int[] Matrixpower (int[] m,intp) { -         int[] res =New int[M.length] [M[0].length]; -         //set res as the unit matrix +          for(inti=0;i<res.length;i++){ -Res[i][i]=1; +         } A          at         int[] temp =m; -          for(;p!=0;p>>=1){ -             if((p&1)!=0){ - Mulimatrix (res, temp); -             } - Mulimatrix (temp, temp); in              -         } to         returnRes; +     } -      the      *     //2 multiplication of matrices $      Public int[] Mulimatrix (int[] M1,int[] m2) {Panax Notoginseng         int[] res =New int[M1.length] [M2[0].length]; -          for(inti=0;i<m1.length;i++){ the              for(intj=0;j<m2[0].length;j++){ +                  for(intk=0;k<m2.length;k++){ ARES[I][J] + = m1[i][k]*M2[k][j]; the                 } +             } -         } $         returnRes; $}

Fibonacci Issues (Java)