I am trying to write code that calculates the right number of happy numbers between 1 and 1 million. What ends up being the result, however, is that either my output window remains blank and keeps on running, or else I get an output of 0, which is not correct. Does anybody have any suggestions? Here's the code that I'm using:

From the main function:

for (x = 2; x < 10; x++)
{
    if(is_happy(x) == 1)
        happy_number++;
}

  cout << "There are " << happy_number << " happy prime numbers between 1 and 1 million" << endl;

Note: happy_number starts off with a value of 0;

Then there's the function that calculates whether or not a number is happy:

int is_happy(int x)
{
    int y;
    int ans = 0;
    while (x > 0)
    {
        y = x%10;
        ans += pow(y, 2.0);
        x = x/10;
        ans += pow(x, 2.0);
    }

    return ans;
 }

Any suggestions?

I used Wikipedia. Happy number

The function named isHappy calculates whether or not the argument is happy. I am not sure if it works right if the argument is a negative integer.

You asked:

How to make a program that finds the number of happy numbers between 1 and 1 million

Function int happyNumbersBetween1_1000000() returns with the number of happy numbers between 1 and 1 000 000.

#include <iostream>

int happy(int i){
    int j=0;
    while(i!=0){
        j+=(i%10)*(i%10);
        i-=(i%10);
        i/=10;
    }
    return j;
}

bool isHappy(int i){
    switch(i){
        case 1: return true;
        case 4: return false;
        default: return isHappy(happy(i));
    }
}

int happyNumbersBetween1_1000000(){
    int j=0;
    for(int i=1; i<=1000000; ++i)
        if(isHappy(i)){
            ++j;
           // std::cout<<i<<std::endl;
        }
    return j;
}

int main()
{
    for(int i=1; i<100; ++i)
        if(isHappy(i))
            std::cout<<i<<" ";
    std::cout<<std::endl;

    std::cout<<happyNumbersBetween1_1000000()<<std::endl;

    return 0;
}

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