Answer to Question #153234 in C++ for Hiba mostafa

Question

consider the following sequence given by the recurrences realtion :

U1=-1 U2=1 U3=2 UN =(2*Un-1 ) - (5*Un-2) +(Un-3 +2) if (n>3)

write a program that enters an integer value n and then prints the value of n-th term Un and then sum of Un

Answer 1

#include <iostream>

int U(int n)
{
    switch(n)
    {
        case 1 : return -1;
        case 2 : return 1;
        case 3 : return 2;
        default: return 2 * U(n-1) - 5 * U(n-2) + 2 + U(n-3);
    }
}

int main()
{
    int n;
    std::cout << "Input integer: ";
    std::cin >> n;
    
    if(n < 1)
    {
        std::cout << "Invalid integer value\n";
        return 1;
    }

    std::cout << "U(" << n << ") = " << U(n) << "\n";

    int sum = 0;
    for(int i=1; i<n; ++i)
    {
        sum += U(i);
    }

    std::cout << "Sum U(" << n << ") = " << sum << "\n";
    
    return 0;
}