Remove Duplicates in C, C++, Java & Python – Code with Explanation & Examples in Short and Simple

   

C Program

#include <stdio.h>
#include <string.h>
int main() {
    char str[100], res[100];
    int i, j, k = 0, found;
    printf("Enter a string: ");
    gets(str);
    for(i = 0; str[i]; i++) {
        found = 0;
        for(j = 0; j < k; j++) if(res[j] == str[i]) found = 1;
        if(!found) res[k++] = str[i];
    }
    res[k] = '\0';
    printf("String without duplicates: %s", res);
    return 0;
}

C Output

Input: programming
Output: progamin

C++ Program

#include <iostream>
#include <string>
using namespace std;
int main() {
    string str, res="";
    cout<<"Enter a string: ";
    cin>>str;
    for(char c: str) if(res.find(c)==string::npos) res+=c;
    cout<<"String without duplicates: "<<res;
}

C++ Output

Input: success
Output: suce

JAVA Program

import java.util.*;
class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        String str = sc.next();
        String res = "";
        for(char c: str.toCharArray()) 
            if(res.indexOf(c) == -1) res += c;
        System.out.println("String without duplicates: " + res);
    }
}

JAVA Output

Input: banana
Output: ban

Python Program

s = input("Enter a string: ")
res = ""
for c in s:
    if c not in res:
        res += c
print("String without duplicates:", res)

Python Output

Input: Mississippi
Output: Misp

In-Depth Explanation

Example

Consider the word "programming". Upon close inspection, certain characters such as 'r', 'g', and 'm' repeat. Duplicates removed would imply we retain the first instance of a character and ignore repetitions. Thus "programming" turns into "progamin". The principle is merely to see if a character is already in the result; if not, we add it.

Real-Life Analogy

Think of creating a guest list for a party. There are occasions when the name of a person may be written twice in error. But when you reach the door, you want unique names on the invitation card only. So you remove the duplicates and retain only one record of each guest. Likewise, in strings, duplicates are identical names, and our program is like the doorkeeper who prevents any repetition.

Why It Matters

Duplicate removal is a principle of basic data processing. Whether cleaning raw data, handling lists of users, or sanitizing database entries, duplicate removal guarantees efficiency and accuracy. In programming, mastering this exercise develops intuition into iteration, conditional checks, and string manipulation—basics for every coder.

Learning Insights

Beginners learn how to use loops to iterate over every character and how to keep track of what has been encountered before. They also learn from string immutability in Java and Python, where you construct a new string instead of modifying the original string. In C and C++, it teaches you character arrays and indexing, which solidify logical reasoning regarding memory and array positions.

Real-World Applications

This issue is commonly applied in fields such as data cleansing, search, and user verification. As an example, when users input tags for a blog post, the duplicate is not needed; it is automatically filtered out by the system. Likewise, in database systems, redundancy can lead to errors, and the reasoning of this program can be broadened to identify and stop redundancy.

Interview Relevance

Interviewers ask duplicate removal questions most of the time because it is a test of string manipulation, awareness of time complexities, and problem-solving strategies. A junior programmer may attempt nested loops (O(n²)), while a more advanced programmer may utilize a set or hash map for quicker output (O(n)). This provides candidates with the opportunity to demonstrate a brute-force solution as well as an efficient one.

SEO Optimized Closing

Knowing how to eliminate duplicate characters from a string is a fundamental skill for those learning to program. It can help learners acquire logical thinking, handling strings, and data cleaning in actual applications. With practice in solving this problem in C, C++, Java, and Python, the learners are assured of developing confidence in codewriting efficiency in preparation for coding interviews and exams. Whether you are a fresher attempting to learn the strings manipulation basics or getting ready for technical interviews in companies, learning duplicate removal improves your problem-solving capacity and assists in constructing robust software solutions.