Text Pyramid using recursion in Java

Question

I am trying to make a full triangle with any text input. Example if I have string that is "abcdefghij" I want the result to be

    aj
   abij
  abchij
 abcdghij
abcdefghij

if the string length is odd as in "abcdefghij" then the output would be

    a
   abi
  abchi
 abcdghi
abcdefghi

Here is what I have so far but my output for the words is upside down. My output is

    abcdefghij
   abcdghij
  abchij
 abij
aj

What I have done so far

public static void main(String[] args) {

        solve("abcdefghij");

    }

    public static void solve(String word) {

        solve(word, word.length()/2-1);

    }

    public static void solve(String word, int it) {

        // print starting spaces
        for(int i = 0; i < it; i++)
            System.out.print(" ");

        // print out string
        System.out.print(word+"\n");


        if(word.length() > 2) {

            int newlengthperside = (word.length() - 2)/2;
            solve( word.substring(0, newlengthperside) + word.substring(word.length() - newlengthperside), it-1);

        }
    }

I just need a suggestion on how to start from aj instead of the end. Thanks for any help. This is homework so just a hint is appreciated.

Answer 1

Swap your "//print out string" line with your recursive call:

public static void solve(String word, int it) {
    if(word.length() > 2) {
        int newlengthperside = (word.length() - 2)/2;
        solve( word.substring(0, newlengthperside) + word.substring(word.length() - newlengthperside), it-1);
    }
    // print out string
    System.out.print(word+"\n");
}

This will output the shortest string first, then as the function returns, it'll output the next largest word, and so on up the chain. You'll have to work out the spaces part yourself, but this should give you a start (I think the existing loop placed between the recursion and the "//print out string" areas will work).

Answer 2

You code should look like this :

 public void solve(String str) {
    for(int i=1;i<=str.length()/2;i++) {
        for(int j=str.length()/2-i; j>0 ;j--) {
            System.out.print(" ");
        }
        System.out.print(str.substring(0,i));
        System.out.print(str.substring(str.length()-i));
        System.out.println();
    }
}

Input :

"abcdefghij"

Output:

    aj
   abij
  abchij
 abcdghij
abcdefghij

This only covers the happy path but you show understand the logic.

EDIT :

For recursive approach :

public static void solve(String word) {
    solve(word, 0);
}

public static void solve(String word, int it) {

    // print starting spaces
    String spaces="";
    for(int i = 0; i < it; i++)
        spaces+=" ";


    if(word.length() > 2) {
        int newlengthperside = (word.length() - 2)/2;
        solve(word.substring(0, newlengthperside) + word.substring(word.length() - newlengthperside), it + 1);
    }
    System.out.print(spaces+word+"\n");
}

I changed a few things:
1. counting number of spaces needed and putting them in a string which is used later on.

String spaces="";
for(int i = 0; i < it; i++)
  spaces+=" ";

2. solve(word, 0); //-> 0 from length

3. solve(word.substring(0, newlengthperside) + word.substring(word.length() - newlengthperside), it + 1); //-> adding 1 to the length

Input :

solve("abcdefghij");

Output :

    aj
   abij
  abchij
 abcdghij
abcdefghij