Searching: Fibonaccian Search-2: N+1 is NOT a perfect Fibonacci number
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Algorithm F
Algorithm F (Fibonaccian search). Given a table of records R1R2 … RN whose
keys are in increasing order K1 < K2 < … < KN, this algorithm searches for a
given argument K.
In this case, N + 1 is not a perfect Fibonacci number, Fk+1. It is not difficult to make
the method work for arbitrary N, if a suitable initialization is provided (see exercise 14).
One idea is to find the least M>=0 such that N+M has the form Fk+1-1.
F1. [Initialize.] Set i <– Fk - M, p <– Fk-1, q <– Fk-2. (Throughout the algorithm,
p and q will be consecutive Fibonacci numbers.)
F2. [Compare.] If i<=0, go to F4; If K < Ki, go to step F3; if K > Ki, go to F4; and if K = Ki,
the algorithm terminates successfully.
F3. [Decrease i.] If q = 0, the algorithm terminates unsuccessfully. Otherwise
set i <– i-q, and set (p, q) <– (q, p-q); then return to F2.
F4. [Increase i.] If p = 1, the algorithm terminates unsuccessfully. Otherwise
set i <– i + q, p <– p - q, then q <– q - p, and return to F2. |
Java program
In this program, R1,…,RN were simplified to K1,…,KN.
/** * Created with IntelliJ IDEA. * User: 1O1O * Date: 12/11/13 * Time: 6:52 PM * :)~ * Fibonaccian Search-2:N+1 is NOT a perfect Fibonacci number:Searching */public class Main { public static void main(String[] args) { int N = 16; int[] K = new int[17]; /*Prepare the ordered data table*/ K[1] = 61; K[2] = 87; K[3] = 154; K[4] = 170; K[5] = 275; K[6] = 426; K[7] = 503; K[8] = 509; K[9] = 512; K[10] = 612; K[11] = 653; K[12] = 677; K[13] = 703; K[14] = 765; K[15] = 897; K[16] = 908; /*Output sorted Ks*/ System.out.println("Sorted Ks:"); for(int i=1; i<=N; i++){ System.out.println(i+":"+K[i]); } System.out.println(); /*Kernel of the Algorithm!*/ int Key = 653; /*Key to be found*/ /*Fibonacci number:0,1,1,2,3,5,8,13,21,34,55...*/ /*Fn = Fn-1 + Fn-2, F0 = 0, F1 = 1...*/ /*In this case: N+1=17 is not a perfect Fibonacci number then, find the least M>=0 such that N+M has the form Fk+1-1 and obviously the M is 4, N+M=20=F8-1=Fk+1-1, then k=7 then i=Fk-M=F7-4=13-4=9, p=Fk-1=F6=8, q=Fk-2=F5=5*/ int i = 9; int p = 8; int q = 5; do{ if(i<=0 || Key > K[i]){ if(p == 1){ System.out.println("Outputs: "+Key+" not found."); break; }else { i = i+q; p = p-q; q = q-p; } }else if(Key < K[i]){ if(q == 0){ System.out.println("Outputs: "+Key+" not found."); break; }else { i = i-q; int temp = q; q = p-q; p = temp; } }else { System.out.println("Outputs: "+Key+" in K["+i+"]."); break; } }while (true); }}
Outputs
Sorted Ks:1:612:873:1544:1705:2756:4267:5038:5099:51210:61211:65312:67713:70314:76515:89716:908Outputs: 653 in K[11].
Reference
<< The art of computer programming: Sorting and Searching >> VOLUME 3, DONALD E. KNUTH