String to Integer in Different Programming Languages

Last Updated : 23 Jul, 2025

Below are example programs to do string to integer conversion in different programming languages.

C++

#include <bits/stdc++.h>
using namespace std;

int main()
{
    int val;
    char strn1[] = "12546";

    val = atoi(strn1);
    cout << "String value = " << strn1 << endl;
    cout << "Integer value = " << val << endl;

    char strn2[] = "GeeksforGeeks";
    val = atoi(strn2);
    cout << "String value = " << strn2 << endl;
    cout << "Integer value = " << val << endl;

    return (0);
}

// This code is contributed by shivanisinghss2110

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

int main()
{
    int val;
    char strn1[] = "12546";

    val = atoi(strn1);
    printf("String value = %s\n", strn1);
    printf("Integer value = %d\n", val);

    char strn2[] = "GeeksforGeeks";
    val = atoi(strn2);
    printf("String value = %s\n", strn2);
    printf("Integer value = %d\n", val);

    return (0);
}

Java

import java.util.*;

public class Main {
    public static void main(String[] args)
    {
        int val;
        String strn1 = "12546";

        val = Integer.parseInt(strn1);
        System.out.println("String value = " + strn1);
        System.out.println("Integer value = " + val);

        String strn2 = "GeeksforGeeks";
        try {
            val = Integer.parseInt(strn2);
            System.out.println("String value = " + strn2);
            System.out.println("Integer value = " + val);
        }
        catch (NumberFormatException e) {
            val = 0;
            System.out.println("String value = " + strn2);
            System.out.println("Integer value = " + val);
        }
    }
}

Python

def main():
    strn1 = "12546"
    val = int(strn1)
    print("String value = ", strn1)
    print("Integer value = ", val)

    strn2 = "GeeksforGeeks"
    try:
        val = int(strn2)
    except ValueError:
        val = 0
        print("String value = ", strn2)
        print("Integer value = ", val)


if __name__ == "__main__":
    main()

using System;

namespace GeeksforGeeks {
class Program {
    static void Main(string[] args)
    {
        String strn1 = "12546";
        int val = int.Parse(strn1);
        Console.WriteLine("String value = " + strn1);
        Console.WriteLine("Integer value = " + val);

        String strn2 = "GeeksforGeeks";
        try {
            val = int.Parse(strn2);
        }
        catch (FormatException e) {
            val = 0;
            Console.WriteLine("String value = " + strn2);
            Console.WriteLine("Integer value = " + val);
        }
    }
}
}

JavaScript

// Javascript code to convert string to integer
let val;
let strn1 = "12546";

val = parseInt(strn1);
console.log("String value = " + strn1);
console.log("Integer value = " + val);

let strn2 = "GeeksforGeeks";
val = parseInt(strn2);
console.log("String value = " + strn2);
console.log("Integer value = " + val);

// This code is contributed by prasad264

Output

String value = 12546
Integer value = 12546
String value = GeeksforGeeks
Integer value = 0

Complexity Analysis of Standard Functions

Below is a typical time complexity analysis of the library functions

Time Complexity: O(n), Only one traversal of the string is needed.
Space Complexity: O(1), As no extra space is required.

Detailed Articles for Different Languages:

Below are detailed articles in different programming languages to do string to integer conversion.

String to Integer in C/C++
String to Integer in Java
String to Integer in JavaScript
String to Integer in Python
String to Integer in C#
String to Integer in PHP

How to implement your own conversion?

We need to write a function that takes a string as an argument and returns its equivalent integer value. Please refer the below post for details.

Write your own string to integer converter.

Integer literal in C/C++ (Prefixes and Suffixes)

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String to Integer in Different Programming Languages

Complexity Analysis of Standard Functions

Detailed Articles for Different Languages:

How to implement your own conversion?

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