Question

(Java - Stack) Describe a nonrecursive algorithm for enumerating all permutations of the numbers {1,2, . . . ,n} using an explicit stack.

Answer 1

Implementation of procedure combination which accepts the two parameters and calculates the permutations of the numbers {1,2 … n}

Algorithm:

Step 1: Start

Step 2: Create a procedure combination which accepts two parameters n and k as a type of integers.

Step 2.1: Declare an output as an array as a type of integer with size n.

Step 2.2: Declare stkPtr as stack<int> type and initialize the stkPtr.

Step 2.3: Push the initially value 0 to stack through stack object stkPtr.

Step 2.4: Iterate loop through while, check the Count of the stack is greater than zero.

Step 2.4.1: Declare indexflag as a type of integer variable and assign the resultant value of stkPtr.Count -1 to indexflag.

Step 2.4.2: Declare popValue as a type of integer variable and assign the resultant value of stkPtr.Pop() to popValue.

Step 2.4.3: Iterate the loop popValue is less than k then

Step 2.4.3.1: Assign the pre-increment value of popValue to output[indexflag++].

Step 2.4.3.2: push the popValue into stack object stkPtr.

Step 2.4.3.3: check indexflag is equal to n then

                        Step 2.4.3.3.1: return the output.

                        Step 2.4.3.3.2 : break the loop through the break statement.

Step 3: End the procedure combination.

Step 4: Call the procedure combination from the main method with appropriate parameters n and k.

Step 5: Stop.