Randomized quick sort (Java implementation)

Randomized quicksort (Randomized quick sort)

• Running time is independent of input ordering.
• No assumption about the input distribution. (no assumptions are made on the input sequence distribution)
• No specific input elicit the worst-case behavior. (No specific input causes the worst operating efficiency)
• Worst-case determined only by a random-number generator. (worst case is determined by the random number generator)
• Pivot a random element. (Randomly select one of the main elements)

The pseudo-code in the fast-sequenced randomized sample in the introduction to the algorithm is as follows:

Partitioning of arrays:

1 randomized-PARTITION (A, P, r)2 i = RANDOM (p, r)3Exchange A[r] with a[ I]4return PARTITION (A, p, R)

where partition (A, p, R) reference Quick sort (Java implementation)

1 randomized-QUICKSORT (A, P, r)2     if p < r3         q = randomized-PARTITION (A, p, r)4         randomized-quicksort (A, p, q-1)5         Randomized-quicksort (A, q+1, R)

Random fast sorting, randomly selecting a principal and array division: Randomquicksort.java

1  Packagequicksort;2 3 ImportJava.util.Random;4 5  Public classRandomquicksort {6 7      Public voidSort (int[] A,intPintr) {8         if(P <r) {9             intQ =Partition (A, p, r);TenSort (A, p, q-1); OneSort (a,q+1, R);  A         } -     } -      the     Private intPartition (int[] A,intPintr) { -         /*random selection of the main element*/ -Random random =NewRandom (); -         intRandom_index = Random.nextint (r-p+1) +p; +System.out.println ("random_index=" +random_index); -         inttemp =A[random_index]; +A[random_index] =A[r]; AA[R] =temp; at          -         intx = A[r];//pivot = a[p] -         inti = P-1; -          for(intj = P; J < R; J + +) { -             if(A[j] <= x) {//Comparison with pivot -i++; in                 intTMP =A[j]; -A[J] =A[i]; toA[i] =tmp; +             } -         } the          *         intTMP =A[r]; $A[r] = a[i+1];Panax NotoginsengA[I+1] =tmp; -          the         returnI+1; +          A     } the      +}

Quick ordering of test randomization: Randomquicksorttest.java

1  Packagequicksort;2 3  Public classRandomquicksorttest {4 5 //Static int[] A ={2, 8, 7, 1, 3, 5, 6, 4};6     Static int[] A ={13, 19, 9, 5, 12, 8, 7, 4, 21, 2, 6, 11};7      Public Static voidMain (string[] args) {8Randomquicksort Randomquicksort =NewRandomquicksort ();9Randomquicksort.sort (A, 0, a.length-1);Ten          One          for(inti = 0; i < a.length; i++) { ASystem.out.print (a[i]+ ""); -         } -     } the}

Test results:

random_index=2random_index=2random_index=0random_index=0random_index =8  Random_index=10random_index=7random_index

Randomized quick sort (Java implementation)