Question

Write a function in C++ that takes an integer argument D and returns the index and value of the first D-digit Lucas number. Turn in a print-out of your code, as well as the index and value your function returns when D = 15. Example) Let D = 3. The first 3-digit Lucas Number is L10 = 123, so your function should return something like firstDDigitLucas(3) = (10, 123).

Answer 1

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Code

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#include <iostream>

using namespace std;

void lucas(long long);    //function to get lucas numbers
int noOfDigit(long long); // function number of digits in a number

int main()
{

long long n;
cout<<"Enter No. of digits = ";
cin>>n;
lucas(n);

return 0;
}

void lucas(long long n)
{

long long a=2;
long long b=1;
long long temp;
int index=1;
while(1)
{
    temp=a+b;
    a=b;
    b=temp;
    index++;

    int d=noOfDigit(temp);

    if(n==d)
    {
       cout<<"firstDDigitLucas("<<n<<") = "<<"("<<index<<","<<temp<<")"<<endl;
       return;

    }

}

}

int noOfDigit(long long temp)
{

int digits = 0;
while (temp != 0)
    {
temp /= 10;
digits++;
}

return digits;

}

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Output

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