Concatenation of Two Strings (original) (raw)

Last Updated : 31 Oct, 2024

String concatenation is the process of joining two strings end-to-end to form a single string.

**Examples

**Input: s1 = “Hello”, s2 = “World”
**Output: “HelloWorld”
**Explanation: Joining “Hello” and “World” results in “HelloWorld”.

**Input: s1 = “Good”, s2 = “Morning”
**Output: “GoodMorning”
**Explanation: Joining “Good” and “Morning” results in “GoodMorning”

Using + Operator

Almost all languages support + operator to concatenate two strings. In C, we have a library function strcat() for the same purpose.

C++ `

#include #include

using namespace std;

int main() { string s1 = "Hello, "; string s2 = "World!";

// Concatenating the strings
string res = s1 + s2;

cout << res << endl;
return 0;

}

C

#include <stdio.h> #include <string.h>

int main() { char s1[50] = "Hello, "; char s2[] = "World!";

// Concatenating the strings
strcat(s1, s2);

printf("%s\n", s1);
return 0;

}

Java

public class GfG { public static void main(String[] args) { String s1 = "Hello, "; String s2 = "World!";

    // Concatenating the strings
    String res = s1 + s2;
    
    System.out.println(res);
}

}

Python

s1 = "Hello, " s2 = "World!"

Concatenating the strings

res = s1 + s2

print(res)

C#

using System;

class Program { static void Main() { string s1 = "Hello, "; string s2 = "World!";

    // Concatenating the strings
    string res = s1 + s2;
    
    Console.WriteLine(res);
}

}

JavaScript

let s1 = "Hello, "; let s2 = "World!";

// Concatenating the strings let res = s1 + s2;

console.log(res);

`

Write your Own Method

• Create an empty result string.
• Traverse through s1 and append all characters to result.
• Traverse through s2 and append all characters to result. C++ `

#include #include using namespace std;

string concat(string s1, string s2) { string res;

// Append s1 to res
for (char c : s1) {
    res += c;
}

// Append s2 to res
for (char c : s2) {
    res += c;
}

return res;

}

int main() { string s1 = "Hello, "; string s2 = "World!";

// Call the function to concatenate the strings
string res = concat(s1, s2);

cout << res << endl;

return 0;

}

C

#include <stdio.h> #include <string.h>

void concat(const char* s1, const char* s2, char* res) { // Append s1 to res while (*s1) { *res++ = *s1++; }

// Append s2 to res
while (*s2) {
    *res++ = *s2++;
}
*res = '\0';

}

int main() { const char* s1 = "Hello, "; const char* s2 = "World!"; char res[100];

// Call the function to concatenate the strings
concat(s1, s2, res);

printf("%s\n", res);
return 0;

}

Java

import java.util.StringBuilder;

public class Main { public static String concat(String s1, String s2) { StringBuilder res = new StringBuilder();

    // Append s1 to res
    for (char c : s1.toCharArray()) {
        res.append(c);
    }
    
    // Append s2 to res
    for (char c : s2.toCharArray()) {
        res.append(c);
    }
    
    return res.toString();
}

public static void main(String[] args) {
    String s1 = "Hello, ";
    String s2 = "World!";
    
    // Call the function to concatenate the strings
    String res = concat(s1, s2);
    
    System.out.println(res);
}

}

Python

def concat(s1, s2): res = ''

# Append s1 to res
for c in s1:
    res += c

# Append s2 to res
for c in s2:
    res += c

return res

if name == 'main': s1 = 'Hello, ' s2 = 'World!'

# Call the function to concatenate the strings
res = concat(s1, s2)

print(res)

C#

using System;

class Program { static string Concat(string s1, string s2) { string res = "";

    // Append s1 to res
    foreach (char c in s1) {
        res += c;
    }

    // Append s2 to res
    foreach (char c in s2) {
        res += c;
    }

    return res;
}

static void Main() {
    string s1 = "Hello, ";
    string s2 = "World!";

    // Call the function to concatenate the strings
    string res = Concat(s1, s2);

    Console.WriteLine(res);
}

}

JavaScript

function concat(s1, s2) { let res = '';

// Append s1 to res
for (let c of s1) {
    res += c;
}

// Append s2 to res
for (let c of s2) {
    res += c;
}

return res;

}

let s1 = 'Hello, '; let s2 = 'World!'; let res = concat(s1, s2); console.log(res);

`

Time Complexity : O(m + n) where m and n are lengths of the two strings.