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Write a C# program for a given string S which may contain lowercase and uppercase characters. The task is to remove all duplicate characters from the string and find the resultant string.
Note: The order of remaining characters in the output should be the same as in the original string.
Example:
Input: Str = horje
Output: geksfor
Explanation: After removing duplicate characters such as e, k, g, s, we have string as “geksfor”.
Input: Str = HappyNewYear
Output: HapyNewYr
Explanation: After removing duplicate characters such as p, e, a, we have string as “HapyNewYr”.
Naive Approach:
Iterate through the string and for each character check if that particular character has occurred before it in the string. If not, add the character to the result, otherwise the character is not added to result.
Below is the implementation of above approach:
C#
using System;
using System.Collections.Generic;
class GFG {
static String removeDuplicate(char[] str, int n)
{
int index = 0;
for (int i = 0; i < n; i++) {
int j;
for (j = 0; j < i; j++) {
if (str[i] == str[j]) {
break;
}
}
if (j == i) {
str[index++] = str[i];
}
}
char[] ans = new char[index];
Array.Copy(str, ans, index);
return String.Join("", ans);
}
public static void Main(String[] args)
{
char[] str = "horje".ToCharArray();
int n = str.Length;
Console.WriteLine(removeDuplicate(str, n));
}
}
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Output:
geksfor
Time Complexity : O(n * n)
Auxiliary Space : O(1) , Keeps order of elements the same as input.
Remove duplicates from a given string using Hashing
Iterating through the given string and use a map to efficiently track of encountered characters. If a character is encountered for the first time, it’s added to the result string, Otherwise, it’s skipped. This ensures the output string contains only unique characters in the same order as the input string.
Below is the implementation of above approach:
C#
using System;
using System.Collections.Generic;
public class GFG {
static char[] removeDuplicates(char[] s, int n)
{
Dictionary<char, int> exists
= new Dictionary<char, int>();
String st = "";
for (int i = 0; i < n; i++) {
if (!exists.ContainsKey(s[i])) {
st += s[i];
exists.Add(s[i], 1);
}
}
return st.ToCharArray();
}
public static void Main(String[] args)
{
char[] s = "horje".ToCharArray();
int n = s.Length;
Console.Write(removeDuplicates(s, n));
}
}
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Output:
geksfor
Time Complexity: O(n)
Auxiliary Space: O(n)
Please refer complete article on Remove duplicates from a given string for more details!
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