C++ :: Recursive Function - Take Number And Return With All Sevens Turned Into Eights

Task: Write a recursive function `seven_up` which takes a number and returns that number with all the sevens turned into eights.

- Example

cout<<seven_up(777)<<endl; //prints 888
cout<<seven_up(1234567890)<<endl; //prints 1234568890
cout<<seven_up(50)<<endl; //prints 50

- Hint: It's like removeFirst, except:

0. Base Case: If the number is one digit long, we don't want to erase it (by returning 0). Instead, riddle me this: When I have a one-digit number, what happens if I change all the 7's into 8's? Well, if the number is 7, it becomes 8, but otherwise it's unchanged.

1. Recursive Call: If the number is longer, then we strip off the last digit, figure out what the answer for the rest is (the recursive call on n/10), and then put the last digit back on the number when you're done.

Hint: You probably need to store the least digit (the n%10) and check if it's 7 separately.

#include <iostream>
using namespace std;
int removeFirst(int n) {
if(n<10)
return 0;
return 10*removeFirst(n/10)+n%10;

[Code] ......

I tried other algorithms but i don't get it.