How to reverse a string sentence (only words, not characters) without using the C# "string built-in" functions
Reverse of a string sentence
Introduction
This article represents one of few ways of reversal of string sentence (only words, without using any inbuilt c# functions except String.Length property as author feels lazy to write code for it.)
Background
Knowledge of control structures (for
, foreach
, while
) and data types (char
, string
).
Using the code
There are mainly three functions created :
ReverseString( String )
: returns reversed string, e.g.,ReverseString("Hello How are you")
.Split( String )
: returns a string array containing words and spaces at consecutive places.ReturnSpace( int )
: accepts an integer representing number of spaces, creates and return a string containing specified number of spaces.
/**Reverse a Sentence without using C# inbuilt functions
(except String.Length property, m not going to write code for this small functionality )*/
const char EMPTYCHAR = ' ';
const string EMPTYSTRING = " ";
/// <summary>
/// Reverse a string Sentence
/// </summary>
/// <param name="pStr"></param>
/// <returns></returns>
public string ReverseString(string pStr)
{
if (pStr.Length > 1) //can be checked/restricted via validation
{
string strReversed = String.Empty;
string[] strSplitted = new String[pStr.Length];
int i;
strSplitted = Split(pStr); // Complexity till here O(n)
for (i = strSplitted.Length - 1; i >= 0; i--)
// this for loop add O(length of string) in O(n) which is similar to O(n)
{
strReversed += strSplitted[i];
}
return strReversed;
}
return pStr;
}
/// <summary>
/// Split the string into words & empty spaces
/// </summary>
/// <param name="str"></param>
/// <returns></returns>
public string[] Split(string str)
{
string strTemp = string.Empty;
string[] strArryWithValues = new String[str.Length];
int j = 0;
int countSpace = 0;
//Complexity of for conditions result to O(n)
foreach (char ch in str)
{
if (!ch.Equals(EMPTYCHAR))
{
strTemp += ch; //append characters to strTemp
if (countSpace > 0)
{
strArryWithValues[j] = ReturnSpace(countSpace); // Insert String with Spaces
j++;
countSpace = 0;
}
}
else
{
countSpace++;
if (countSpace == 1)
{
strArryWithValues[j] = strTemp; // Insert String with Words
strTemp = String.Empty;
j++;
}
}
}
strArryWithValues[j] = strTemp;
return (strArryWithValues);
}
/// <summary>
/// Return a string with number of spaces(passed as argument)
/// </summary>
/// <param name="count"></param>
/// <returns></returns>
public string ReturnSpace(int count)
{
string strSpaces = String.Empty;
while (count > 0)
{
strSpaces += EMPTYSTRING;
count--;
}
return strSpaces;
}
/************Reverse Sentence Ends***************/
Points of Interest
Maintaining complexity to O(n) where n is length of string.