Find first and last digits of a number

09 Jun, 2022
Given a number and to find first and last digit of a number.Examples:  
Input : 12345 
Output : First digit: 1
         last digit : 5

Input : 98562
Output : First digit: 9
         last digit : 2
 
To find last digit of a number, we use modulo operator %. When modulo divided by 10 returns its last digit. Suppose if n = 1234 then last Digit = n % 10 => 4 To finding first digit of a number is little expensive than last digit. To find first digit of a number we divide the given number by 10 until number is greater than 10. At the end we are left with the first digit. 
Approach 1 (With loop):
C++
Java
Python3
C#
PHP
Javascript
// Program to find first and last// digits of a number#include <bits/stdc++.h>using namespace std;  // Find the first digitint firstDigit(int n){    // Remove last digit from number    // till only one digit is left    while (n >= 10)         n /= 10;          // return the first digit    return n;}  // Find the last digitint lastDigit(int n){    // return the last digit    return (n % 10);}  // Driver programint main(){    int n = 98562;    cout << firstDigit(n) << " "         << lastDigit(n) << endl;    return 0;}
// Java Program to find first and last// digits of a numberimport java.util.*;import java.lang.*;  public class GfG{          // Find the first digit    public static int firstDigit(int n)    {        // Remove last digit from number        // till only one digit is left        while (n >= 10)             n /= 10;              // return the first digit        return n;    }      // Find the last digit    public static int lastDigit(int n)    {        // return the last digit        return (n % 10);    }          // driver function    public static void main(String argc[])    {        int n = 98562;        System.out.println(firstDigit(n) + " "        + lastDigit(n));    }}  // This code is contributed by Sagar Shukla
# Python3 program to find first and # last digits of a number  # Find the first digitdef firstDigit(n) :      # Remove last digit from number    # till only one digit is left    while n >= 10:         n = n / 10;          # return the first digit    return int(n)  # Find the last digitdef lastDigit(n) :      # return the last digit    return (n % 10)  # Driver Coden = 98562;print(firstDigit(n), end = " ") print(lastDigit(n))  # This code is contributed by rishabh_jain
// C# Program to find first and last// digits of a numberusing System;  public class GfG{          // Find the first digit    public static int firstDigit(int n)    {        // Remove last digit from number        // till only one digit is left        while (n >= 10)             n /= 10;              // return the first digit        return n;    }      // Find the last digit    public static int lastDigit(int n)    {        // return the last digit        return (n % 10);    }          // driver function    public static void Main()    {        int n = 98562;        Console.WriteLine(firstDigit(n) + " "        + lastDigit(n));    }}  // This code is contributed by vt_m
<?php// PHP Program to find first // and last digits of a number  // Find the first digitfunction firstDigit($n){    // Remove last digit from number    // till only one digit is left    while ($n >= 10)         $n /= 10;          // return the first digit    return (int)$n;}  // Find the last digitfunction lastDigit($n){    // return the last digit    return ((int)$n % 10);}  // Driver Code$n = 98562;echo firstDigit($n) . " " .     lastDigit($n) . "\n";  // This code is contributed // by Akanksha Rai(Abby_akku)
<script>// javascript Program to find first and last// digits of a number      // Find the first digit    function firstDigit(n)    {        // Remove last digit from number        // till only one digit is left        while (n >= 10)             n /= 10;                // return the first digit        return Math.floor(n);    }        // Find the last digit    function lastDigit(n)    {        // return the last digit        return Math.floor(n % 10);    }  // Driver code           let n = 98562;        document.write(firstDigit(n) + " "        + lastDigit(n));    // This code is contributed by sanjoy_62.</script>
9 2

Time Complexity: O(log10n)Auxiliary Space: O(1) 
Approach 2 (Without loop) 
C++
Java
Python3
C#
PHP
Javascript
// Program to find first and last // digits of a number#include <bits/stdc++.h>using namespace std;  // Find the first digitint firstDigit(int n){    // Find total number of digits - 1    int digits = (int)log10(n);      // Find first digit    n = (int)(n / pow(10, digits));      // Return first digit    return n;}  // Find the last digitint lastDigit(int n){    // return the last digit    return (n % 10);}  // Driver programint main(){    int n = 98562;    cout << firstDigit(n) << " "          << lastDigit(n) << endl;    return 0;}
// Java program to find first and // last  digits of a numberimport java.math.*;  class GFG {          // Find the first digit    static int firstDigit(int n)    {        // Find total number of digits - 1        int digits = (int)(Math.log10(n));              // Find first digit        n = (int)(n / (int)(Math.pow(10, digits)));              // Return first digit        return n;    }          // Find the last digit    static int lastDigit(int n)    {        // return the last digit        return (n % 10);    }          // Driver program    public static void main(String args[])    {        int n = 98562;        System.out.println(firstDigit(n) +                           " " + lastDigit(n));    }}    // This code is contributed by Nikita Tiwari.
# Python3 program to find first  # and last digits of a numberimport math  # Find the first digitdef firstDigit(n) :          # Find total number of digits - 1    digits = (int)(math.log10(n))      # Find first digit    n = (int)(n / pow(10, digits))      # Return first digit    return n;  # Find the last digitdef lastDigit(n) :          # return the last digit    return (n % 10)  # Driver Coden = 98562;print(firstDigit(n), end = " ") print(lastDigit(n))  # This code is contributed by rishabh_jain
// C# program to find first and // last digits of a numberusing System;  class GFG {          // Find the first digit    static int firstDigit(int n)    {        // Find total number of digits - 1        int digits = (int)(Math.Log10(n));              // Find first digit        n = (int)(n / (int)(Math.Pow(10, digits)));              // Return first digit        return n;    }          // Find the last digit    static int lastDigit(int n)    {        // return the last digit        return (n % 10);    }          // Driver program    public static void Main()    {        int n = 98562;        Console.WriteLine(firstDigit(n) +                        " " + lastDigit(n));    }}    // This code is contributed by vt_m.
<?php// Program to find first and last // digits of a number   // Find the first digit function firstDigit($n) {     // Find total number of digits - 1     $digits = (int)log10($n);       // Find first digit     $n = (int)($n / pow(10, $digits));       // Return first digit     return $n; }   // Find the last digit function lastDigit($n) {     // return the last digit     return ($n % 10); }   // Driver Code $n = 98562; echo firstDigit($n) , " ",     lastDigit($n), "\n";   // This code is contributed by ajit?>
<script>  // JavaScript program to find first  // and last digits of a number  // Find the first digitfunction firstDigit(n){          // Find total number of digits - 1    let digits = Math.floor(Math.log(n)/Math.log(10))      // Find first digit    n = Math.floor(n / Math.pow(10, digits))      // Return first digit    return n;}  // Find the last digitfunction lastDigit(n){          // return the last digit    return (n % 10)}  // Driver Codelet n = 98562;document.write(firstDigit(n)," ") document.write(lastDigit(n),"</br>")  // This code is contributed by shinjanpatra  </script>
9 2

Time Complexity: O(1)Auxiliary Space: O(1)
Important note: log10() is a mathematical function present in math.h header file. It returns log base 10 value of the passed parameter to log10() function. 
jit_t
Akanksha_Rai
sanjoy_62
shinjanpatra
singhh3010
number-digits
number-theory
Mathematical
number-theory
Mathematical
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