CODEWITHSUNDEEP
javarecursion
mikecal7
mikecal7

Reputation: 95

Trouble using recursion to print out converging and diverging sequence of numbers

The wording of the problem is "Write a method writeSequence that accepts an integer n as a parameter and prints a symmetric sequence of n numbers with descending integers ending in 1 followed by ascending integers beginning with 1, as in the table below:"

The table is essentially:

1 = 1
2 = 1 1
3 = 2 1 2
4 = 2 1 1 2
5 = 3 2 1 2 3
6 = 3 2 1 1 2 3

My attempted code is 

public void writeSequence(int n){
    if (n < 1){
        throw new IllegalArgumentException();
    }
    if (n == 1){
        System.out.print(n + " ");
    }
    else if (n == 2){
        System.out.print(1 + " " + 1 + " ");
    }
    else if (n % 2 == 0){
        System.out.print(n - (n/2) + " ");
        writeSequence(n - (n/2));
        System.out.print(n - (n/2) + " ");
    }
    else{
        System.out.print(n-(n/2) + " ");
        writeSequence(n - 2 );
        System.out.print(n-(n/2)+ " ");
    }
}

For inputs 1-10, my code is not generating the correct answer for 6, 8, and 10. Any help is greatly appreciated.

Edit:

Fixed spelling in title

Edit 2:

My results are

1 = 1
2 = 1 1 
3 = 2 1 2
4 = 2 1 1 2
5 = 3 2 1 2 3
6 = 3 2 1 2 3 (wrong)
7 = 4 3 2 1 2 3 4
8 = 4 2 1 1 2 4 (wrong)
9 = 5 4 3 2 1 2 3 4 5
10 = 5 3 2 1 2 3 5 (wrong)

If someone could show me where I have made an error in my code that would be great!

Upvotes: 0

Views: 315

Answers (1)

Bohemian
Bohemian

Reputation: 424953

Your recursive call passes the incorrect value. Each time the algorithm recurses, it should decrease the value by 2.

Change this:

writeSequence(n - (n/2));

to this:

writeSequence(n - 2);

Upvotes: 2

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