- C++ Programming Examples
- C++ Programming Examples
- C++ Hello World
- C++ Get Input
- C++ Print Integer
- C++ Add Two Numbers
- C++ Add Sub Mul Div
- C++ Add Digits
- C++ Find Average Perc
- C++ Find Arithmetic Mean
- C++ Sum of n Natural Numbers
- C++ Sum of n Numbers
- C++ Area Perimeter of Square
- C++ Area Perimeter of Rectangle
- C++ Area Perimeter of Triangle
- C++ Area Circum of Circle
- C++ Find Simple Interest
- C++ Fahrenheit to Celsius
- C++ Celsius to Fahrenheit
- C++ Print Prime Numbers
- C++ Reverse a Number
- C++ Swap Two Numbers
- C++ Print Multiplication Table
- C++ Find Factorial of Number
- C++ Find Factors of Number
- C++ Find HCF & LCM
- C++ Make Calculator
- C++ Count Digits in Number
- C++ Sum of First & Last Digit
- C++ Product of Digits of Number
- C++ Sum of Squares of Digits
- C++ Interchange Digits of Number
- C++ if else Programs
- C++ Check Even or Odd
- C++ Check Prime or Not
- C++ Check Alphabet or Not
- C++ Check Vowel or Not
- C++ Check Leap Year or Not
- Check Reverse equal Original
- C++ Check Perfect Number
- C++ Check Palindrome or Not
- C++ Check Armstrong or Not
- C++ Divisibility Test
- C++ Find Wage of Labor
- C++ Find Discounted Price
- C++ Find Shipping Charge
- C++ Find Telephone Bills
- C++ Calculate Student Grade
- C++ Largest of Two Numbers
- C++ Largest of Three Numbers
- C++ Number Conversion
- C++ Decimal to Binary
- C++ Decimal to Octal
- C++ Decimal to Hexadecimal
- C++ Binary to Decimal
- C++ Binary to Octal
- C++ Binary to Hexadecimal
- C++ Octal to Decimal
- C++ Octal to Binary
- C++ Octal to Hexadecimal
- C++ Hexadecimal to Decimal
- C++ Hexadecimal to Binary
- C++ Hexadecimal to Octal
- C++ Pattern Programs
- C++ Pattern Programs
- C++ Print Diamond Pattern
- C++ Print Floyd's Triangle
- C++ Print Pascal's Triangle
- C++ Array Programs
- C++ 1D Array Program
- C++ Linear Search
- C++ Binary Search
- Find Largest Element in Array
- Find Smallest Element in Array
- Find Second Largest Element
- Find Second Smallest Element
- C++ Sum of All Elements
- C++ Multiply All Elements
- C++ Element on Even Position
- C++ Element on Odd Position
- C++ Print Even Numbers in Array
- C++ Print Odd Numbers in Array
- C++ Count Even/Odd Numbers
- C++ Sum of Even/Odd Numbers
- C++ Count Positive Negative Zero
- C++ Reverse an Array
- C++ Insert Element in Array
- C++ Delete Element from Array
- C++ Merge two Arrays
- C++ Bubble Sort
- C++ Selection Sort
- C++ Insertion Sort
- C++ Common Elements
- C++ 2D Array Programs
- C++ Add Two Matrices
- C++ Subtract Two Matrices
- C++ Transpose Matrix
- C++ Multiply Two Matrices
- C++ 3D Array Programs
- C++ String Programs
- C++ Print String
- C++ Find Length of String
- C++ Compare Two Strings
- C++ Copy String
- C++ Concatenate String
- C++ Reverse a String
- C++ Delete Vowels from String
- C++ Delete Word from String
- C++ Count Character in String
- C++ Count Word in String
- C++ Frequency of Word
- C++ Remove Spaces from String
- C++ Sort a String
- C++ Uppercase to Lowercase
- C++ Lowercase to Uppercase
- C++ Swap Two Strings
- C++ Check Anagram or Not
- C++ Capitalize All Words in String
- C++ Capitalize Specific Character
- C++ Get Numbers from String
- C++ File Programs
- C++ Read a File
- C++ Write Content to File
- C++ Append Data in File
- C++ Read & Display File
- C++ Copy a File
- C++ Merge Two Files
- Count Characters, Words in File
- C++ Capitalize All Words in File
- C++ List Files in Directory
- C++ Delete a File
- C++ Encrypt & Decrypt a File
- C++ Misc Programs
- C++ Print ASCII Value
- C++ Add Binary Numbers
- C++ Generate Random Numbers
- C++ Print Smiling Face
- C++ Days into Years, Months
- Add Two Numbers using Pointer
- C++ Print Fibonacci Series
- Generate Armstrong Numbers
- C++ Find nCr and nPr
- C++ Get IP Address
- C++ Print Date/Time
- C++ Shutdown, Restart Computer
- C++ Programming Tutorial
- C++ Tutorial
- C++ Programming Test
- C++ Programming Test
- Give Online Test
- All Test List
C++ Program to Check Armstrong Number
In this article, you will learn and get code to check whether an input number is an armstrong number or not in C++. The program is created in these ways:
- Check Armstrong Number using while loop
- Check Armstrong Number using for loop
But before starting these programs, let's first understand about Armstrong number.
What is an Armstrong Number ?
A number that equals to the sum of its own digits, where each digit raised to the power of number of digits. For example, 1634 is an Armstrong number, because:
1634 = 14 + 64 + 34 + 44 = 1 + 1296 + 81 + 256 = 1297 + 337 = 1634
The result is equal to the number itself. So it is an Armstrong number.
Note - Because the total number of digit in 1634 is 4, so each of its digit raised to the power of 4.
Check Armstrong Number using while Loop
This is the first program of this article. It asks from user to enter a number and checks whether it is an Armstrong number or not.
The question is, write a program in C++ that checks whether a given number by user at run-time, is an Armstrong number or not. Here is its answer:
#include<iostream> using namespace std; int main() { intnum, temp, noOfDigit=0, res=0, rem, pow, i; cout<<"Enter the Number: "; cin>>num; temp = num; while(num>0) { num = num/10; noOfDigit++; } num = temp; while(num>0) { rem = num%10; pow = 1; i = 0; while(i<noOfDigit) { pow = pow*rem; i++; } res = res + pow; num = num/10; } if(res==temp) cout<<"\nIt is an Armstrong Number"; else cout<<"\nIt is not an Armstrong Number"; cout<<endl; return 0; }
This program was build and run under Code::Blocks IDE. Here is its sample run:
Now supply any number say 1634 and press ENTER
key to check whether it is an Armstrong
number or not as shown in the snapshot given below:
And here is another sample run, with user input, 153:
Note - Because 153 is a 3-digit number, therefore each digit will raised to the power of 3
The following block of code:
while(num>0)
{
num = num/10;
noOfDigit++;
}
is used to count total number of digits available in the given number.
The dry run of above program with user input, 153 goes like:
- Initial values, noOfDigit=0, res=0
- After entering the number at run-time, say 153. It gets stored in num. So num=153
- Using
temp=num;
, the value of num gets initialized to temp. So temp=153 - Now the condition of while loop gets evaluated
- That is, the condition, num>0 or 153>0 evaluates to be true, therefore program flow goes inside the loop And num/10 or 153/10 or 15 gets initialized to num. So num=15
- The value of noOfDigit gets incremented. So noOfDigit=1 (because its initial value is 0)
- Program flow goes back and evaluates the condition of while loop again
- The process continues until its condition evaluates to be false. Before its condition evaluated to be false, the value of num and noOfDigit will be 0 and 3. So noOfDigit=3
- Now the statement
num = temp;
initializes the value of temp to num. So num=153 - The condition of second while loop gets evaluated. That is, the condition num>0 or 153>0 evaluates to be true, therefore program flow goes inside the loop
- There num%10 or 153%10 or 3 gets initialized to rem. So rem=3
- And pow=1, i=0
- Now the condition of third while loop gets evaluated. That is, the condition, i<noOfDigit or 0<3 evaluates to be true, therefore program flow goes inside the loop
- And pow*rem or 1*3 or 3 gets initialized to pow
- The value of i gets incremented. So i=1
- Program flow goes back and evaluates the condition, i<noOfDigit again
- The process continues until its condition evaluates to be false
- Before its condition evaluated to be false, the value of pow will be 27. That is the result of 33
- So the statement,
res = res + pow;
initializes the value of res + pow (or 0+27 or 27) to res. So res=27 - Finally num/10 or 153/10 or 15 gets initialized to num. So num=15
- Program flow again goes back and evaluates the condition, num>0 (of while loop) again
- The process continues, until its condition evaluates to be false
- After its condition evaluated to be false, the value of res will be 153
- And after exiting from the loop, do compare res with original value entered by user
- If both is equal, then it is an Armstrong number, otherwise it is not an Armstrong number
Check Armstrong Number using for Loop
Now let's create the same program as of previous one, using for loop. That is, this program does the same job as of previous program. The only difference is, in place of while loop, we've used for loop here:
#include<iostream> using namespace std; int main() { intnum, temp, noOfDigit=0, res=0, rem, pow, i; cout<<"Enter the Number: "; cin>>num; for(temp=num; temp>0; temp=temp/10) noOfDigit++; for(temp=num; temp>0; temp=temp/10) { rem = temp%10; pow = 1; for(i=0; i<noOfDigit; i++) pow = pow*rem; res = res + pow; } if(res==num) cout<<"\nIt is an Armstrong Number"; else cout<<"\nIt is not an Armstrong Number"; cout<<endl; return 0; }
This program produces exactly the same output as of previous program. Here is its sample run with user input, 371:
And here is the last sample run, with user input, 567:
Same Program in Other Languages
« Previous Program Next Program »