Randomization of Algs4-2.3.29

2.3.29 randomization. Empirical studies are used to compare the effects of random selection of sharding elements and randomization of arrays at the beginning of the text. Switch when the sub-array size is m, and sort the non-repeated arrays whose size is n, where M = 10, 20, and 50, n = 10 ^ 3, 10 ^ 4, 10 ^ 5, and 10 ^ 6.
A: Because the generated array to be sorted is already randomized, it takes time for method 1 to disrupt the array before sorting. Therefore, method 1 takes longer than method 2, therefore, when the array to be sorted is randomization, the comparison between the two methods is not particularly strong.

Public class e2d3d29
{
Public static void main (string [] ARGs)
{
Int nlen [] = {1000,10000, 100000,000000 };
Int mlen [] = {10, 20, 50 };
For (INT ni = 0; Ni <nlen. length; Ni ++)
{
Int n = nlen [Ni];
For (int mi = 0; Mi <mlen. length; Mi ++)
{
Int M = mlen [MI];
Double s1times = 0.0;
Double s2times = 0.0;
For (INT time = 0; time <10; time ++)
{
Double [] a1 = new double [N];
Double [] a2 = new double [N];
For (INT I = 0; I <n; I ++)
{
A1 [I] = stdrandom. Random ();
A2 [I] = A1 [I];
}
Stopwatch timer1 = new stopwatch ();
E2d3d29s1. Sort (A1, M );
S1times = s1times + timer1.elapsedtime ();
//
Stopwatch timer2 = new stopwatch ();
E2d3d29s2. Sort (A2, M );
S2times = s2times + timer2.elapsedtime ();
}
Stdout. printf ("n = % 7D, M = % 2D, shuffleelapsedtime = %. 3f, randomelapsedtime = %. 3f, shuffle-random = %. 3f \ n ", n, m, s1times/10, s2times/10, (s1times + s2times)/10 );
}
} // End for Ni
} // End main
} // End class

Public class e2d3d29s1
{
Public static void sort (comparable [] A, int m)
{
Stdrandom. Shuffle ();
Sort (A, 0, A. Length-1, M );
}

Private Static void sort (comparable [] A, int Lo, int hi, int m)
{
If (Hi-Lo + 1 <m)
{
Insertsort (A, lo, hi );
Return;
}
Int J = partition (A, lo, hi );

Sort (A, lo, J-1, M );
Sort (A, J + 1, hi, M );
}

Private Static int partition (comparable [] A, int Lo, int hi)
{
Int I = Lo, j = Hi + 1;
Comparable v = A [lo];
While (true)
{
While (less (A [++ I], V) if (I = Hi) break;
While (less (V, A [-- J]) if (j = LO) break;

If (I> = J) break;
Exch (A, I, j );
}
Exch (A, lo, J );
Return J;
}

Private Static void insertsort (comparable [] A, int Lo, int hi)
{
For (INT I = lo + 1; I {
For (Int J = I; j> 0 & less (A [J], a [J-1]); j --)
Exch (A, J, J-1 );
}
}

Private Static Boolean less (comparable V, comparable W)
{Return v. compareto (w) <0 ;}

Private Static void exch (comparable [] A, int I, Int J)
{
Comparable T = A [I];
A [I] = A [J];
A [J] = T;
}

Private Static void show (comparable [])
{
For (INT I = 0; I <A. length; I ++)
Stdout. Print (A [I] + "");
Stdout. println ();
}

Public static Boolean issorted (comparable [])
{
For (INT I = 1; I <A. length; I ++)
If (less (A [I], a [I-1]) return false;
Return true;
}
Public static void main (string [] ARGs)
{
Int n = integer. parseint (ARGs [0]);
Double [] A = new double [N];
For (int K = 0; k <n; k ++)
A [k] = stdrandom. Random ();
Sort (A, 10 );
Stdout. println ("issorted =" + issorted ());
}
}


Public class e2d3d29s2
{
Public static void sort (comparable [] A, int m)
{
Sort (A, 0, A. Length-1, M );
}

Private Static void sort (comparable [] A, int Lo, int hi, int m)
{
If (Hi-Lo + 1 <m)
{
Insertsort (A, lo, hi );
Return;
}
Int J = partition (A, lo, hi );

Sort (A, lo, J-1, M );
Sort (A, J + 1, hi, M );
}

Private Static int partition (comparable [] A, int Lo, int hi)
{
Int I = Lo, j = Hi + 1;
Exch (A, lo, stdrandom. Uniform (Lo, hi + 1 ));
Comparable v = A [lo];
While (true)
{
While (less (A [++ I], V) if (I = Hi) break;
While (less (V, A [-- J]) if (j = LO) break;

If (I> = J) break;
Exch (A, I, j );
}
Exch (A, lo, J );
Return J;
}

Private Static void insertsort (comparable [] A, int Lo, int hi)
{
For (INT I = lo + 1; I {
For (Int J = I; j> 0 & less (A [J], a [J-1]); j --)
Exch (A, J, J-1 );
}
}

Private Static Boolean less (comparable V, comparable W)
{Return v. compareto (w) <0 ;}

Private Static void exch (comparable [] A, int I, Int J)
{
Comparable T = A [I];
A [I] = A [J];
A [J] = T;
}

Private Static void show (comparable [])
{
For (INT I = 0; I <A. length; I ++)
Stdout. Print (A [I] + "");
Stdout. println ();
}

Public static Boolean issorted (comparable [])
{
For (INT I = 1; I <A. length; I ++)
If (less (A [I], a [I-1]) return false;
Return true;
}
Public static void main (string [] ARGs)
{
Int n = integer. parseint (ARGs [0]);
Double [] A = new double [N];
For (int K = 0; k <n; k ++)
A [k] = stdrandom. Random ();
Sort (A, 10 );
Stdout. println ("issorted =" + issorted ());
}
}

Randomization of Algs4-2.3.29