Remove Duplicate Characters
Hard
C++
Strings
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Problem Statement
Remove all duplicate characters, keep only first occurrence.
Real Life: Unique character extraction.
Real Life: Unique character extraction.
Input Format
A string S.
Output Format
String after removing duplicate characters
(only first occurrence kept).
(only first occurrence kept).
Example
programming
progamin
Constraints
• String length ≥ 1
• Case-sensitive (a and A are different)
• Maintain original order
• Case-sensitive (a and A are different)
• Maintain original order
Concept Explanation
Duplicate characters are removed,
but the first occurrence of each character is kept.
This is useful when extracting unique characters.
but the first occurrence of each character is kept.
This is useful when extracting unique characters.
Step-by-Step Explanation
1.Take input string S.
2.Create a boolean array of size 256 (for all ASCII characters).
3.Initialize all values as false.
4.Traverse the string from left to right.
5.For each character ch:
• If visited[ch] is false:
• Print ch.
• Mark visited[ch] = true.
• Else:
• Skip the character.
6.Continue till end of string.
2.Create a boolean array of size 256 (for all ASCII characters).
3.Initialize all values as false.
4.Traverse the string from left to right.
5.For each character ch:
• If visited[ch] is false:
• Print ch.
• Mark visited[ch] = true.
• Else:
• Skip the character.
6.Continue till end of string.
Concept Explanation
Duplicate characters are removed,
but the first occurrence of each character is kept.
This is useful when extracting unique characters.
but the first occurrence of each character is kept.
This is useful when extracting unique characters.
Step-by-Step Explanation
1.Take input string S.
2.Create a boolean array of size 256 (for all ASCII characters).
3.Initialize all values as false.
4.Traverse the string from left to right.
5.For each character ch:
• If visited[ch] is false:
• Print ch.
• Mark visited[ch] = true.
• Else:
• Skip the character.
6.Continue till end of string.
2.Create a boolean array of size 256 (for all ASCII characters).
3.Initialize all values as false.
4.Traverse the string from left to right.
5.For each character ch:
• If visited[ch] is false:
• Print ch.
• Mark visited[ch] = true.
• Else:
• Skip the character.
6.Continue till end of string.
Input / Output Format
Input Format
A string S.
Output Format
String after removing duplicate characters
(only first occurrence kept).
(only first occurrence kept).
Constraints
• String length ≥ 1
• Case-sensitive (a and A are different)
• Maintain original order
• Case-sensitive (a and A are different)
• Maintain original order
Examples
Input:
programming
Output:
progamin
Example Solution (Public)
void string_q12_remove_duplicates() {
string text = "programming";
string result = "";
bool seen[256] = {false};
cout << "Original: " << text << endl;
for(int i = 0; i < text.length(); i++) {
if(!seen[text[i]]) {
result += text[i];
seen[text[i]] = true;
}
}
cout << "After removing duplicates: " << result << endl;
}
Official Solution Code
void string_q12_remove_duplicates() {
string text = "programming";
string result = "";
bool seen[256] = {false};
cout << "Original: " << text << endl;
for(int i = 0; i < text.length(); i++) {
if(!seen[text[i]]) {
result += text[i];
seen[text[i]] = true;
}
}
cout << "After removing duplicates: " << result << endl;
}
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