Check if two strings are same or not without using library functions
Last Updated :
23 Jul, 2025
Given two strings S1 and S2, the task is to check whether they are the same or not without using string library functions.
Examples:
Input: S1 = ”GeeksForGeeks”, S2 = ”GeeksForGeeks”
Output:
True
Explanation:
S1 and S2 are the same strings
Input: S1 = ”GeeksForGeeks”, S2 = ”GeeksforGeeks”
Output:
False
Approach: Follow the steps below to solve the problem:
- Create a function compareStrings() that takes the two strings S1 and S2 as input parameters and does the following:
- If the lengths of S1 and S2 are different, return false.
- Store the length of S1 in a variable, say N.
- Traverse from 0 to N-1 using the variable i and do the following:
- If S1[i] is not equal to S2[i], return false.
- Return true at the end of the traversal.
Below is the implementation of the above approach:
C
#include <stdbool.h>
#include <stdio.h>
// Function to calculate length of string
int len(char* S)
{
// Variable for traversal
int i = 0;
// Traverse till null is reached
while (S[i])
i++;
return i;
}
// Function to check whether
// two strings are same or not
bool compareStrings(char S1[], char S2[])
{
// If lengths of the two
// strings are different
if (len(S1) != len(S2))
return false;
// Variable for traversal
int i = 0;
// Traverse till null is reached
while (S1[i]) {
if (S1[i] != S2[i])
return false;
// Increment i
i++;
}
return true;
}
// Driver Code
int main()
{
// Input
char S1[] = "GeeksForGeeks";
char S2[] = "GeeksForGeeks";
// Function Call
bool ans = compareStrings(S1, S2);
printf("%s", ans ? "True" : "False");
return 0;
}
// C++ program for the above approach
#include <iostream>
#include <cstring>
using namespace std;
// Function to calculate length of string
int len(char* S)
{
// Variable for traversal
int i = 0;
// Traverse till null is reached
while (S[i])
i++;
return i;
}
// Function to check whether
// two strings are same or not
bool compareStrings(char S1[], char S2[])
{
// If lengths of the two
// strings are different
if (len(S1) != len(S2))
return false;
// Variable for traversal
int i = 0;
// Traverse till null is reached
while (S1[i]) {
if (S1[i] != S2[i])
return false;
// Increment i
i++;
}
return true;
}
// Driver Code
int main()
{
// Input
char S1[] = "GeeksForGeeks";
char S2[] = "GeeksForGeeks";
// Function Call
bool ans = compareStrings(S1, S2);
cout << (ans ? "True" : "False");
return 0;
}
// This code is contributed by rishab
// Java program to implement the above approach
public class Main {
// Function to calculate length of string
public static int len(String S) {
// Variable for traversal
int i = 0;
// Traverse till null is reached
while (i < S.length())
i++;
return i;
}
// Function to check whether
// two strings are same or not
public static boolean compareStrings(String S1, String S2) {
// If lengths of the two
// strings are different
if (len(S1) != len(S2))
return false;
// Variable for traversal
int i = 0;
// Traverse till null is reached
while (i < S1.length()) {
if (S1.charAt(i) != S2.charAt(i))
return false;
// Increment i
i++;
}
return true;
}
// Driver Code
public static void main(String[] args) {
// Input
String S1 = "GeeksForGeeks";
String S2 = "GeeksForGeeks";
// Function Call
boolean ans = compareStrings(S1, S2);
System.out.println(ans ? "True" : "False");
}
}
// Contributed by adityashae15
# Function to check whether
# two strings are same or not
def compareStrings(S1, S2):
# If lengths of the two
# strings are different
if (len(S1) != len(S2)):
return False
# Variable for traversal
i = 0
# Traverse till null is reached
while (i < len(S1)):
if (S1[i] != S2[i]):
return False
# Increment i
i += 1
return True
# Driver Code
if __name__ == '__main__':
# Input
S1 = "GeeksForGeeks"
S2 = "GeeksForGeeks"
# Function Call
ans = compareStrings(S1, S2)
print("True" if ans else "False")
# This code is contributed by mohit kumar 29
<script>
function len(S)
{
// Variable for traversal
let i = 0;
// Traverse till null is reached
while (i < S.length)
i++;
return i;
}
function compareStrings(S1,S2)
{
// If lengths of the two
// strings are different
if (len(S1) != len(S2))
return false;
// Variable for traversal
let i = 0;
// Traverse till null is reached
while (i < S1.length)
{
if (S1[i] != S2[i])
return false;
// Increment i
i++;
}
return true;
}
// Input
let S1 = "GeeksForGeeks";
let S2 = "GeeksForGeeks";
// Function Call
let ans = compareStrings(S1, S2);
document.write(ans ? "True" : "False");
// This code is contributed by patel2127
</script>
using System;
using System.Collections.Generic;
class GFG{
// Function to calculate length of string
static int len(string S)
{
// Variable for traversal
int i = 0;
// Traverse till null is reached
while (i < S.Length)
i++;
return i;
}
// Function to check whether
// two strings are same or not
static bool compareStrings(string S1, string S2)
{
// If lengths of the two
// strings are different
if (len(S1) != len(S2))
return false;
// Variable for traversal
int i = 0;
// Traverse till null is reached
while (i < S1.Length)
{
if (S1[i] != S2[i])
return false;
// Increment i
i++;
}
return true;
}
// Driver Code
public static void Main()
{
// Input
string S1 = "GeeksForGeeks";
string S2 = "GeeksForGeeks";
// Function Call
bool ans = compareStrings(S1, S2);
Console.Write(ans ? "True" : "False");
}
}
// This code is contributed by SURENDRA_GANGWAR
Time Complexity: O(N)
Auxiliary Space: O(1)
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