[jira] [Comment Edited] (GROOVY-11655) Create extension method to make StringBuilder like a stack

[Paul King (Jira)]

    [ 
https://issues.apache.org/jira/browse/GROOVY-11655?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17950160#comment-17950160
 ] 

Paul King edited comment on GROOVY-11655 at 5/8/25 1:34 AM:
------------------------------------------------------------

The other Groovy idiomatic way to solve this would be to create a custom stack:
{code:groovy}
class TextEditor {
    private left = new StringBuilderStack(),
            right = new StringBuilderStack()

    void addText(String text) {
         left.append(text)
    }

    int deleteText(int k) {
        [k, left.size()].min().tap{ left.length -= it }
    }

    String cursorLeft(int k) {
        while (k > 0 && left) {
            right.push(left.pop())
            k--
        }
        text()
    }

    String cursorRight(int k) {
        while (k > 0 && right) {
            left.push(right.pop())
            k--
        }
        text()
    }

    private String text() {
        left.takeRight(10)
    }
}

class StringBuilderStack extends Stack<Character> {
    private @Delegate StringBuilder sb = new StringBuilder()

    @Override
    Character push(Character ch) {
        sb.append(ch)
        ch
    }

    @Override
    Character peek() {
        sb[-1]
    }

    @Override
    Character pop() {
        char last = sb[-1]
        sb.length -= 1
        last
    }

    void setLength(int length) {
        sb.setLength(length)
    }

    int getLength() {
        sb.length()
    }

    @Override
    int size() {
        sb.size()
    }
}

new TextEditor().with {
    addText('leetcode')                    // leetcode|
    assert deleteText(4) == 4              // leet|
    addText('practice')                    // leetpractice|
    assert cursorRight(3) == 'etpractice'  // leetpractice|
    assert cursorLeft(8) == 'leet'         // leet|practice
    assert deleteText(10) == 4             // |practice
    assert cursorLeft(2) == ''             // |practice
    assert cursorRight(6) == 'practi'      // practi|ce
}
{code}


was (Author: paulk):
The other Groovy idiomatic way to solve this would be to create a custom stack:
{code:groovy}
class TextEditor {
    private left = new StringBuilderStack(),
            right = new StringBuilderStack()

    void addText(String text) {
         left.append(text)
    }

    int deleteText(int k) {
        [k, left.size()].min().tap{ left.length -= it }
    }

    String cursorLeft(int k) {
        while (k > 0 && left) {
            right.push(left.pop())
            k--
        }
        text()
    }

    String cursorRight(int k) {
        while (k > 0 && right) {
            left.push(right.pop())
            k--
        }
        text()
    }

    private String text() {
        left.takeRight(10)
    }
}

class StringBuilderStack extends Stack<Character> {
    private @Delegate StringBuilder sb = new StringBuilder()

    Character push(Character ch) {
        sb.append(ch)
        ch
    }

    Character peek() {
        sb[-1]
    }

    Character pop() {
        char last = sb[-1]
        sb.length -= 1
        last
    }

    void setLength(int length) {
        sb.setLength(length)
    }

    int getLength() {
        sb.length()
    }

    int size() {
        sb.size()
    }
}

new TextEditor().with {
    addText('leetcode')                    // leetcode|
    assert deleteText(4) == 4              // leet|
    addText('practice')                    // leetpractice|
    assert cursorRight(3) == 'etpractice'  // leetpractice|
    assert cursorLeft(8) == 'leet'         // leet|practice
    assert deleteText(10) == 4             // |practice
    assert cursorLeft(2) == ''             // |practice
    assert cursorRight(6) == 'practi'      // practi|ce
}
{code}

> Create extension method to make StringBuilder like a stack
> ----------------------------------------------------------
>
>                 Key: GROOVY-11655
>                 URL: https://issues.apache.org/jira/browse/GROOVY-11655
>             Project: Groovy
>          Issue Type: New Feature
>            Reporter: John
>            Priority: Major
>
> for leetcode problem: 
> [https://leetcode.com/problems/design-a-text-editor/description/]
> the java code below,  suppose StringBuilder to be a contain of chars , 
> meanwhile as a stack.
>  
> {code:java}
> class TextEditor {
>     private final StringBuilder left = new StringBuilder(); 
>     private final StringBuilder right = new StringBuilder(); 
>     public void addText(String text) {
>         left.append(text); 
>     }
>     public int deleteText(int k) {
>         k = Math.min(k, left.length());
>         left.setLength(left.length() - k); 
>         return k;
>     }
>     public String cursorLeft(int k) {
>         while (k > 0 && !left.isEmpty()) {
>             right.append(left.charAt(left.length() - 1)); 
>             left.setLength(left.length() - 1);
>             k--;
>         }
>         return text();
>     }
>     public String cursorRight(int k) {
>         while (k > 0 && !right.isEmpty()) {
>             left.append(right.charAt(right.length() - 1)); 
>             right.setLength(right.length() - 1);
>             k--;
>         }
>         return text();
>     }
>     private String text() {
>         
>         return left.substring(Math.max(left.length() - 10, 0));
>     }
> }
> {code}
>  
>  



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