Exam & Solution - A Concise and Practical Introduction to Programming Algorithms in Java - page 228

public static void mysteriousRecursive( int [] tab,
int k) {

if (k == tab . length − 1)

display(tab) ;
for ( int j=k; j < t a b . l e n g t h ; j ++) {

swap3( tab , k , j ) ;
mysteriousRecursive(tab , k + 1) ;
swap3( tab , k , j ) ;

}

}

public static void init( int [] tab) {
for ( int i=0; i < tab . length ; i++)
tab[i]=i+1;

}

public static void main( String [ ] args ) {

int n = Integer . parseInt(args [0]) ;
int [] t = new i n t [n];
init(t);
swap2( t [ 0 ] , t [ n − 1]) ;
mysterious(t , 0) ;
// mysteriousRecursive(t, 0);

}

}

Once this code compiled, what is the result displayed in the console
output by invoking java MysteriousProgram 4 ? Describe explicitly the
program execution steps and its outcome for the general case (for any
given n > 0 )

SOLUTION:
For n = 4, the program displays the following output:
1234
2134
3214
4231

Function init fills array t that is given by reference with values
rangingfrom1to n . Function swap2 performs a permutation on the
copied values of two array cells, and thus does not modify the original
array cells since it works with copies. The array contents order is
therefore preserved. In the mysterious function, the value of k does
not change and denote a cell array. Here, we use function swap3 that
allows one to exchange the contents of two array cells. At the first loop
round, we exchange an array cell with itself. Then, we successively
exchange the contents of the cell with the contents of the following