Java about reversing string

Question

I am confused about how to write a program that reverse the phrase but maintain the index chosen. Like this,

public static void main(String[] args) {
    String string1 = "He is Chinese";

    System.out.println(reverse(string1));
}

private static String reverse(String string) {
    StringBuilder sb = new StringBuilder();
    int length = string.length();
    for(int i=0;i<length;i++) {
        char a = string.charAt(i);
        if(a == ' ') {
            sb.append(a);
        } else {
            int j = i;
            while(j < length && string.charAt(j) != ' ') {
                j++;
            }
            sb.append(ReverseString(string.substring(i, j)));
            i = j-1;
        }
    }
    return sb.toString();
}
private static String ReverseString(String string) {
    StringBuilder sb = new StringBuilder();

    for(int i=string.length()-1;i>=0; i--) {
        sb.append(string.charAt(i));
    }
    return sb.toString();
}

}

the choosen index is C. i want to keep the C in the places, but the other alphabet is reverse.

the output display is eH si esenihC

Remove the chosen index character. Reverse the string and then re-insert the character at the position. — Subir Kumar Sao
– Subir Kumar Sao, Commented Oct 3, 2013 at 7:05
its 'C' .. and how to do it .. im quite blank in reversing string ... — Alin
– Alin, Commented Oct 3, 2013 at 7:09

Stefano Buora · Accepted Answer · 2013-10-03 10:09:05Z

Also if I don't well understand the phrase "maintain the index chosen" I believe that could be your snippets:

public static String reverse( String input ) {
    String[] words = input.split(" ");
    String ret = "";
    for( String word : words) {
        if( ret.length() > 0 ) { ret+=" "; }
        ret += new StringBuilder(word).reverse();
    }
    return ret;
}

Hoping this may help you...Have fun!

Edit: if you want to keep a character in position after words reversing that could be a solution:

public static String reverse(String input, String pivot) {
    String[] words = input.split(" ");
    String ret = "";
    for( int i = 0; i<words.length; i++ ) {
        if (i != 0) { ret += " "; }
        ret += reverse_word(words[i], pivot);
    }
    return ret;
}

public static String reverse_word(String input, String pivot) {
    // warning: split will lose the last occurrence of pivot
    String[] word_parts = input.split(pivot);
    String ret = "";
    for( int i = 0; i<word_parts.length; i++ ) {
        if (i != 0) { ret += pivot; }
        ret += new StringBuilder(word_parts[i]).reverse();
    }
    // check the last one
    ret += input.endsWith(pivot) ? pivot : "";
    return ret;
}

Subhrajyoti Majumder · Accepted Answer · 2013-10-03 07:19:50Z

1

I really did not understand that maintain the index choosen, but if it is reversing string then,

How about it -

private static String reverse(String string) {
    return new StringBuilder(string).reverse().toString();
}

Updation - As you said - and how to keep the 'C' in its own places? like Chinese, the other alphabet is reversing but only "C" is stayed put in its own places.

private static String reverse(String string) {
    if(string==null||string.length()<=1)
         return string;
    return string.subString(0,1)+new StringBuilder(string.subString(1)).reverse().toString();
}

edited Oct 3, 2013 at 7:19

answered Oct 3, 2013 at 7:04

Subhrajyoti Majumder

41.3k13 gold badges84 silver badges103 bronze badges

5 Comments

Alin Over a year ago

and how to keep the 'C' in its own places? like Chinese, the other alphabet is reversing but only "C" is stayed put in its own places.

Jabir Over a year ago

This doesn't addresses his question. @Up voter Please read the question carefully and completely.

Subhrajyoti Majumder Over a year ago

A slight modification - return string.subString(0,1)+new StringBuilder(string.subString(1)).reverse().toString();

Subhrajyoti Majumder Over a year ago

@Jabir firstly thanks for care to comment, question it self is not clear enough, answer is given a better and shotter whay to achive a solution. Also check the comment trail, where it is clarified and answered.

Rahul Over a year ago

@SubhrajyotiMajumder - You could edit your answer instead of posting the modified solution in comments. Answers and comments have their own specific purposes!:)

Bathsheba · Accepted Answer · 2013-10-03 07:31:01Z

0

To avoid getting tangled up here with character indexes, I'd base a solution on the built-in reverse() function in the StringBuilder class, at the expense of performance.

Assume the preservation index is n:

char c = string[n];
StringBuilder sb(string).deleteCharAt(n).reverse().insert(n, c);
return sb.toString();

Finally, this approach would generalise to an array of such preservation indices - use a loop calling deleteCharAt() and a corresponding loop for reinsertion. Do let me know if you need that.

edited Oct 3, 2013 at 7:31

answered Oct 3, 2013 at 7:03

Bathsheba

235k35 gold badges376 silver badges504 bronze badges

1 Comment

Jabir Over a year ago

This doesn't addresses his question

Collectives™ on Stack Overflow

Java about reversing string

3 Answers 3

Comments

5 Comments

1 Comment

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

3 Answers 3

Comments

5 Comments

1 Comment

Your Answer

Sign up or log in

Post as a guest

Related