3) Python program to check if the given number is Happy Number

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A number is said to be happy if it yields 1 when replaced by the sum of squares of its digits repeatedly. If this process results in an endless cycle of numbers containing 4, then the number will be an unhappy number.

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Let's understand by an example:

Number = 32
32+ 22 = 13
12 + 32 = 10
12 + 02 = 1

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In this example, we split 32 to get the sum of squares of its digits which forms another number (13), we replace 32 by 13 to continue this cycle until result 1. We found 32 a happy number.

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If the above cycle for any number results in 1 then that number will be a Happy number otherwise that will be an unhappy number resulting 4, 16, 37, 58, 89, 145, 42, 20,.....

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Some Happy numbers are 7, 28, 100, 320, etc.

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In this program, we need to determine whether the given number is a Happy number or not by following the algorithm below:

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ALGORITHM:

• STEP 1: isHappyNumber() determines whether a given number is happy or not.

  • If the number is greater than 0, then calculate remainder rem by dividing the number with 10.

  • Calculate square of rem and add it to a variable sum.

  • Divide number by 10.

  • Repeat the steps from a to c till the sum of the square of all digits present in number has been calculated.

  • Finally, return the sum.

• STEP 2: Define and initialize variable num.

• STEP 3: Define a variable result and initialize it with a value of num.

• STEP 4: If the result is neither equal to 1 nor 4 then, make a call to isHappyNumber().

• STEP 5: Otherwise, if the result is equal to 1 then, given number is a happy number.

• STEP 6: If the result is equal to 4 then, given number is not a happy number.

#isHappyNumber() will determine whether a number is happy or not    

def isHappyNumber(num):    

    rem = sum = 0;    

    #Calculates the sum of squares of digits    

    while(num > 0):    

        rem = num%10;    

        sum = sum + (rem*rem);    

        num = num//10;    

    return sum;    

num = 82;    

result = num;    

while(result != 1 and result != 4):    

    result = isHappyNumber(result);    

#Happy number always ends with 1    

if(result == 1):    

    print(str(num) + " is a happy number");    

#Unhappy number ends in a cycle of repeating numbers which contain 4    

elif(result == 4):    

    print(str(num) + " is not a happy number");