C++ Program to Find Length of String

Here, you will learn how to find and print the length of any given string by the user at run-time, in C++ language. The program is created with the help of these approaches:

• Find length of string without using any library or built-in function like strlen()
• using strlen() function
• using Pointer

Find Length of String without strlen() Function

To find the length of a string in C++ programming, you have to ask from user to enter the string first. And then find its length as shown in the program given below.

This program finds the length of a string using user-based code. That is, this program does not use library function or built-in function, strlen().

// C++ Find Length of String without strlen() Function

#include<iostream>
#include<stdio.h>
using namespace std;
int main()
{
    char str[200];
    int len=0, i=0;
    cout<<"Enter the String: ";
    gets(str);
    while(str[i])
    {
        len++;
        i++;
    }
    cout<<"\nLength = "<<len;
    cout<<endl;
    return 0;
}

Output

Enter the String: Welcome to Techarge
Lenght=19

Find Length of String using strlen() Function

Here is another C++ program that also finds and prints length of string entered by user. The only difference with previous program is, this program uses a built-in or library function of C++ named strlen().

The function, strlen() takes string as its argument and returns its length. This function is defined in string.h header file.

// C++ Find Length of String using strlen() Function

#include<iostream>
#include<stdio.h>
#include<string.h>
using namespace std;
int main()
{
    char str[200];
    int len=0;
    cout<<"Enter the String: ";
    gets(str);
    len = strlen(str);
    cout<<"\nLength = "<<len;
    cout<<endl;
    return 0;
}

Output

Enter the String: Welcome to Techarge
Lenght=19

Find Length of String using Pointer

Now let’s create the same purpose program, that is to find length of a string, but using pointer. The address of first character of string gets initialized to pointer type variable say ptr and using this variable, the length of string gets calculated.

Note – The & is called as address of operator. Whereas as the * is called as value at operator. The ptr++ (char pointer type variable) moves to next character’s address

// C++ Find Length of String using Pointer

#include<iostream>
#include<stdio.h>
using namespace std;
int main()
{
    char str[200], *ptr;
    int len=0;
    cout<<"Enter the String: ";
    gets(str);
    ptr = &str[0];
    while(*ptr)
    {
        len++;
        ptr++;
    }
    cout<<"\nLength = "<<len;
    cout<<endl;
    return 0;
}

Output

Enter the String: Welcome to Techarge
Lenght=19