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returning a string in reverse

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  • L Luc Pattyn

    Since you already optimized the code, more in particular by unrolling the for loop, it is actually more like O(n/2) which is quite good. :)

    Luc Pattyn [Forum Guidelines] [My Articles]


    this months tips: - before you ask a question here, search CodeProject, then Google - the quality and detail of your question reflects on the effectiveness of the help you are likely to get - use PRE tags to preserve formatting when showing multi-line code snippets


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    Imran Adam
    wrote on last edited by
    #21

    Thanks all sorted, this is what i used....... public string Reverse(string WhatToReverse) { string str2 = string.Empty; StringBuilder sb = new StringBuilder(); //char array char[] myArray = WhatToReverse.ToCharArray(); for(int i = WhatToReverse.Length-1; i >=0; i--) { sb.Append(myArray[i].ToString()); } str2 = sb.ToString(); return str2; }

    Cheers :)

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    • I Imran Adam

      Thanks all sorted, this is what i used....... public string Reverse(string WhatToReverse) { string str2 = string.Empty; StringBuilder sb = new StringBuilder(); //char array char[] myArray = WhatToReverse.ToCharArray(); for(int i = WhatToReverse.Length-1; i >=0; i--) { sb.Append(myArray[i].ToString()); } str2 = sb.ToString(); return str2; }

      Cheers :)

      S Offline
      S Offline
      Skippums
      wrote on last edited by
      #22

      Good work! Post something like this and ask how to make it better, and we will honestly try to help (instead of the crappy roundabout ways we proposed to solve the problem earlier). The way I would implement this problem is as follows...

      public string ReverseString(string str) {
      StringBuilder result = new StringBuilder();
      for (int i = str.Length - 1; i >= 0; --i)
      result.Append(str[i]);
      return result.ToString();
      }

      Like I said, show that you have put even a little effort into trying to find the answer by yourself, and we will try to give you the help you need to get it right, but don't expect us to give you the answer from scratch. Jeff

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      • L Luc Pattyn

        Of course this is homework, no company is going to pay for string reversals. Maybe class gnirts could help, but sadly it has been postponed till the next major upgrade of the .NET Framework. :doh:

        Luc Pattyn [Forum Guidelines] [My Articles]


        this months tips: - before you ask a question here, search CodeProject, then Google - the quality and detail of your question reflects on the effectiveness of the help you are likely to get - use PRE tags to preserve formatting when showing multi-line code snippets


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        Skippums
        wrote on last edited by
        #23

        well played. Jeff

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        • L Luc Pattyn

          Since you already optimized the code, more in particular by unrolling the for loop, it is actually more like O(n/2) which is quite good. :)

          Luc Pattyn [Forum Guidelines] [My Articles]


          this months tips: - before you ask a question here, search CodeProject, then Google - the quality and detail of your question reflects on the effectiveness of the help you are likely to get - use PRE tags to preserve formatting when showing multi-line code snippets


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          Skippums
          wrote on last edited by
          #24

          Wow... I can't beleive I missed that! :laugh: Jeff

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          • I Imran Adam

            Hi Guys i would like to know how you can create a simple method to return a string in reverse order. i have the following method public string myMethod (String myString) { . . //code goes in here . return myString } i have been trying to use a array to read the string into and try that but this doesnt seem to work any ideas please??

            Cheers :)

            A Offline
            A Offline
            Andrei Ungureanu
            wrote on last edited by
            #25

            Have you considered using Array.Reverse method?

            string original = "original";
            char[] reverseString = original.ToCharArray();
            Array.Reverse(reverseString);
            original = string.Empty;
            for (int i = 0; i < reverseString.Length; i++)
            original += reverseString[i];

            I will use Google before asking dumb questions

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            • A Andrei Ungureanu

              Have you considered using Array.Reverse method?

              string original = "original";
              char[] reverseString = original.ToCharArray();
              Array.Reverse(reverseString);
              original = string.Empty;
              for (int i = 0; i < reverseString.Length; i++)
              original += reverseString[i];

              I will use Google before asking dumb questions

              L Offline
              L Offline
              Luc Pattyn
              wrote on last edited by
              #26

              summing up to new string(Array.Reverse(original.ToCharArray()) or even better a sequence of original.ToCharArray(), Array.Reverse() and new string(char[]) :) -- modified at 15:58 Thursday 22nd November, 2007

              Luc Pattyn [Forum Guidelines] [My Articles]


              this months tips: - before you ask a question here, search CodeProject, then Google - the quality and detail of your question reflects on the effectiveness of the help you are likely to get - use PRE tags to preserve formatting when showing multi-line code snippets


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              0
              • S Skippums

                Good work! Post something like this and ask how to make it better, and we will honestly try to help (instead of the crappy roundabout ways we proposed to solve the problem earlier). The way I would implement this problem is as follows...

                public string ReverseString(string str) {
                StringBuilder result = new StringBuilder();
                for (int i = str.Length - 1; i >= 0; --i)
                result.Append(str[i]);
                return result.ToString();
                }

                Like I said, show that you have put even a little effort into trying to find the answer by yourself, and we will try to give you the help you need to get it right, but don't expect us to give you the answer from scratch. Jeff

                G Offline
                G Offline
                Guffa
                wrote on last edited by
                #27

                Just one adjustment; specify the capacity when you create the StringBuilder: StringBuilder result = new StringBuilder(str.Length); This will allocate a string with the exact right size. This has two advantages: 1. The StringBuilder never has to increase the capacity (which is done by allocating a new string with double the size, and copy the data from the previous string to it). 2. The string returned by the ToString method doesn't have any extra unused characters beyond the actual string. If you don't specify the length, the string may use up to twice as much memory as it needs to.

                Experience is the sum of all the mistakes you have done.

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                • L Luc Pattyn

                  summing up to new string(Array.Reverse(original.ToCharArray()) or even better a sequence of original.ToCharArray(), Array.Reverse() and new string(char[]) :) -- modified at 15:58 Thursday 22nd November, 2007

                  Luc Pattyn [Forum Guidelines] [My Articles]


                  this months tips: - before you ask a question here, search CodeProject, then Google - the quality and detail of your question reflects on the effectiveness of the help you are likely to get - use PRE tags to preserve formatting when showing multi-line code snippets


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                  G Offline
                  Guffa
                  wrote on last edited by
                  #28

                  No, you can't do like that. The Array.Reverse method doesn't return the reversed array, it reverses the array in place.

                  Experience is the sum of all the mistakes you have done.

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                  • G Guffa

                    No, you can't do like that. The Array.Reverse method doesn't return the reversed array, it reverses the array in place.

                    Experience is the sum of all the mistakes you have done.

                    L Offline
                    L Offline
                    Luc Pattyn
                    wrote on last edited by
                    #29

                    You're right of course. So I'd better turn it into a small method... :)

                    Luc Pattyn [Forum Guidelines] [My Articles]


                    this months tips: - before you ask a question here, search CodeProject, then Google - the quality and detail of your question reflects on the effectiveness of the help you are likely to get - use PRE tags to preserve formatting when showing multi-line code snippets


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                    • I Imran Adam

                      Hi Guys i would like to know how you can create a simple method to return a string in reverse order. i have the following method public string myMethod (String myString) { . . //code goes in here . return myString } i have been trying to use a array to read the string into and try that but this doesnt seem to work any ideas please??

                      Cheers :)

                      P Offline
                      P Offline
                      Pete OHanlon
                      wrote on last edited by
                      #30

                      Of course, as a quick and dirty hack you could always use a recursive method. I'm not saying you should, but you could. I've seen this done in so many homework assignments and coursework samples.

                      Deja View - the feeling that you've seen this post before.

                      My blog | My articles

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                      • P Pete OHanlon

                        Of course, as a quick and dirty hack you could always use a recursive method. I'm not saying you should, but you could. I've seen this done in so many homework assignments and coursework samples.

                        Deja View - the feeling that you've seen this post before.

                        My blog | My articles

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                        Guffa
                        wrote on last edited by
                        #31

                        The recursive method is pretty neat, actually. Who can resist a one-liner? ;) Not very efficient, though. :)

                        public string Reverse(string value) { return value.Length > 1 ? Reverse(value.Substring(1)) + value.Substring(0, 1) : value; }

                        Experience is the sum of all the mistakes you have done.

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                        • L Luc Pattyn

                          Yep, just like a similar reverse problem[^] it can be solved with a single line of code, much shorter than each of the posts/replies in this thread... :)

                          Luc Pattyn [Forum Guidelines] [My Articles]


                          this months tips: - before you ask a question here, search CodeProject, then Google - the quality and detail of your question reflects on the effectiveness of the help you are likely to get - use PRE tags to preserve formatting when showing multi-line code snippets


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                          PIEBALDconsult
                          wrote on last edited by
                          #32

                          What's a line of code?

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                          0
                          • G Guffa

                            The recursive method is pretty neat, actually. Who can resist a one-liner? ;) Not very efficient, though. :)

                            public string Reverse(string value) { return value.Length > 1 ? Reverse(value.Substring(1)) + value.Substring(0, 1) : value; }

                            Experience is the sum of all the mistakes you have done.

                            P Offline
                            P Offline
                            Pete OHanlon
                            wrote on last edited by
                            #33

                            There you go then. The last step is to turn this into a delegate and you're laughing.

                            Deja View - the feeling that you've seen this post before.

                            My blog | My articles

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                            • P Pete OHanlon

                              There you go then. The last step is to turn this into a delegate and you're laughing.

                              Deja View - the feeling that you've seen this post before.

                              My blog | My articles

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                              G Offline
                              Guffa
                              wrote on last edited by
                              #34

                              Well, delegates can be used in many ways...

                              public string Reverse(string value) {
                              string result = string.Empty;
                              new List(value.ToCharArray()).ForEach(delegate(char c) { result = c.ToString() + result; });
                              return result;
                              }

                              ;)

                              Experience is the sum of all the mistakes you have done.

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