returning a string in reverse
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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 :)
That was a topic in here some time in the last year, do you want to search for it or shall I?
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That was a topic in here some time in the last year, do you want to search for it or shall I?
last year? thats too long time ago. i go back a lil, but not that far. could u please search n let me know, that would be v.helpful
Cheers :)
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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 :)
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BTW this is not my Homework, i have written the lines needed to reverse and display the string in the console. but i cant manage to RETURN a REVERSED String!!
Cheers :)
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BTW this is not my Homework, i have written the lines needed to reverse and display the string in the console. but i cant manage to RETURN a REVERSED String!!
Cheers :)
If you can reverse the string and display it in a console, then it should be pretty easy to return the reversed string.
My current favourite word is: PIE! Good ol' pie, it's been a while.
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BTW this is not my Homework, i have written the lines needed to reverse and display the string in the console. but i cant manage to RETURN a REVERSED String!!
Cheers :)
can anyone help me please ??
Cheers :)
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BTW this is not my Homework, i have written the lines needed to reverse and display the string in the console. but i cant manage to RETURN a REVERSED String!!
Cheers :)
Where is this code? You didn't provide it in your original post. If you have already managed to reverse the string and display it, you must have the reversed string in a variable to be returned from your method. The absence of this code suggests that you haven't written it at all and want someone else to do it for you. This isn't how the site works.
Paul Marfleet "No, his mind is not for rent To any God or government" Tom Sawyer - Rush
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BTW this is not my Homework, i have written the lines needed to reverse and display the string in the console. but i cant manage to RETURN a REVERSED String!!
Cheers :)
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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 :)
hmmmm... does that sound like a homework question? you could use a stack to do this:
public void Main()
{
string foo = "i will do my homework on my own";
string blah = reverseString(foo);
Console.WriteLine(foo);
Console.WriteLine(blah);
}
public void reverseString(string Text)
{
System.Collections.Stack st = new Stack();
foreach (char c in Text)
{
st.Push(c);
}
ArrayList l = new ArrayList();
while (st.Count > 0)
{
l.Add(st.Pop());
}
char[] s = l.ToArray(typeof(char)) as char[];
string RetVal = new string(s);
return RetVal;
}but if you use one of the other 999999999 possibilities to do it it'll be more efficient
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Where is this code? You didn't provide it in your original post. If you have already managed to reverse the string and display it, you must have the reversed string in a variable to be returned from your method. The absence of this code suggests that you haven't written it at all and want someone else to do it for you. This isn't how the site works.
Paul Marfleet "No, his mind is not for rent To any God or government" Tom Sawyer - Rush
OMG... ok then, i created a char array; char[] myArray = new char[m]; //m is the length of array read all the data into the array using; for (int i =0; iCheers :)
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hmmmm... does that sound like a homework question? you could use a stack to do this:
public void Main()
{
string foo = "i will do my homework on my own";
string blah = reverseString(foo);
Console.WriteLine(foo);
Console.WriteLine(blah);
}
public void reverseString(string Text)
{
System.Collections.Stack st = new Stack();
foreach (char c in Text)
{
st.Push(c);
}
ArrayList l = new ArrayList();
while (st.Count > 0)
{
l.Add(st.Pop());
}
char[] s = l.ToArray(typeof(char)) as char[];
string RetVal = new string(s);
return RetVal;
}but if you use one of the other 999999999 possibilities to do it it'll be more efficient
ok this is my method, the loop is not functioning, but i cant see y??? public string Reverse(string WhatToReverse) { int lengthOfArray = WhatToReverse.Length; //char array char[] myArray = new char[lengthOfArray]; for (int i = lengthOfArray; i < 0; i--) { myArray[i] = WhatToReverse[i]; Console.Write(myArray[i]); } return ;//still to complete, but the loop dont work }
Cheers :)
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last year? thats too long time ago. i go back a lil, but not that far. could u please search n let me know, that would be v.helpful
Cheers :)
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ok this is my method, the loop is not functioning, but i cant see y??? public string Reverse(string WhatToReverse) { int lengthOfArray = WhatToReverse.Length; //char array char[] myArray = new char[lengthOfArray]; for (int i = lengthOfArray; i < 0; i--) { myArray[i] = WhatToReverse[i]; Console.Write(myArray[i]); } return ;//still to complete, but the loop dont work }
Cheers :)
hustler2005 wrote:
for (int i = lengthOfArray; i < 0; i--)
I is not less than 0 at the start.
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As just stated, if its not homework and you have working code then post it and someone here will explain the use of the
returnkeyword for you. I still call this out as homework.Of course this is homework, no company is going to pay for string reversals. Maybe
class gnirtscould 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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last year? thats too long time ago. i go back a lil, but not that far. could u please search n let me know, that would be v.helpful
Cheers :)
Another http://www.codeproject.com/script/comments/forums.asp?forumid=1649&ForumID=1649&XtraIDs=1649&searchkw=reverse&sd=24%20Aug%202006&ed=22%20Nov%202007&stype=3&Page=4&select=1810365&df=100&exp=1&mpp=50&fr=13817[^] and another http://www.codeproject.com/script/comments/forums.asp?forumid=1649&ForumID=1649&XtraIDs=1649&searchkw=reverse&sd=24%20Aug%202006&ed=22%20Nov%202007&stype=3&Page=4&select=1793424&df=100&exp=1&mpp=50&fr=14253&tid=1793237[^]
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I must object a little; in C# strings are immutable, so swapping chars isn't the right way...
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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hmmmm... does that sound like a homework question? you could use a stack to do this:
public void Main()
{
string foo = "i will do my homework on my own";
string blah = reverseString(foo);
Console.WriteLine(foo);
Console.WriteLine(blah);
}
public void reverseString(string Text)
{
System.Collections.Stack st = new Stack();
foreach (char c in Text)
{
st.Push(c);
}
ArrayList l = new ArrayList();
while (st.Count > 0)
{
l.Add(st.Pop());
}
char[] s = l.ToArray(typeof(char)) as char[];
string RetVal = new string(s);
return RetVal;
}but if you use one of the other 999999999 possibilities to do it it'll be more efficient
I prefer the following...
public void Main()
{
string str = "I will do my homework on my own";
IntPtr strPtr = Marshal.StringToHGlobalUni(str);
IntPtr resPtr = ReverseString(strPtr);
string res = Marshal.PtrToStringUni(result);
Marshal.FreeHGlobal(strPtr);
Marshal.FreeHGlobal(resPtr);
Console.WriteLine(str);
Console.WriteLine(res);
}public IntPtr ReverseString(IntPtr strPtr)
{
string str = Marshal.PtrToStringUni(strPtr);
char[] strAsCharArray = new char[str.Length];
for (int i = 0; i < str.Length; ++i)
{
strAsCharArray[i] = str[0];
str = str.Substring(1);
}
StringBuilder sb = new StringBuilder(strAsCharArray.Length);
string res = string.Empty;
for (int i = 0; i < str.Length; i += 2)
{
string next = string.Empty;
for (int j = 1; j >= 0; --j)
{
if (i + j == str.Length)
continue;
char c = strAsCharArray[i + j];
next.Insert(0, c.ToString());
res.Insert(1 - j, c.ToString());
}
sb.Append(next);
}
str = sb.ToString();
IntPtr rval = Marshal.StringToHGlobalUni(res);
return rval;
}This is O(n), which is as fast as this operation can be done given how strings are implemented in the system (with a double-linked-list, it can be O(1)). Hope this helps. Jeff
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Another http://www.codeproject.com/script/comments/forums.asp?forumid=1649&ForumID=1649&XtraIDs=1649&searchkw=reverse&sd=24%20Aug%202006&ed=22%20Nov%202007&stype=3&Page=4&select=1810365&df=100&exp=1&mpp=50&fr=13817[^] and another http://www.codeproject.com/script/comments/forums.asp?forumid=1649&ForumID=1649&XtraIDs=1649&searchkw=reverse&sd=24%20Aug%202006&ed=22%20Nov%202007&stype=3&Page=4&select=1793424&df=100&exp=1&mpp=50&fr=14253&tid=1793237[^]
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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I prefer the following...
public void Main()
{
string str = "I will do my homework on my own";
IntPtr strPtr = Marshal.StringToHGlobalUni(str);
IntPtr resPtr = ReverseString(strPtr);
string res = Marshal.PtrToStringUni(result);
Marshal.FreeHGlobal(strPtr);
Marshal.FreeHGlobal(resPtr);
Console.WriteLine(str);
Console.WriteLine(res);
}public IntPtr ReverseString(IntPtr strPtr)
{
string str = Marshal.PtrToStringUni(strPtr);
char[] strAsCharArray = new char[str.Length];
for (int i = 0; i < str.Length; ++i)
{
strAsCharArray[i] = str[0];
str = str.Substring(1);
}
StringBuilder sb = new StringBuilder(strAsCharArray.Length);
string res = string.Empty;
for (int i = 0; i < str.Length; i += 2)
{
string next = string.Empty;
for (int j = 1; j >= 0; --j)
{
if (i + j == str.Length)
continue;
char c = strAsCharArray[i + j];
next.Insert(0, c.ToString());
res.Insert(1 - j, c.ToString());
}
sb.Append(next);
}
str = sb.ToString();
IntPtr rval = Marshal.StringToHGlobalUni(res);
return rval;
}This is O(n), which is as fast as this operation can be done given how strings are implemented in the system (with a double-linked-list, it can be O(1)). Hope this helps. Jeff
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
-
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
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 :)