C++ Number Pong - c++

Question

"Number pong" is what I am trying to do. Ex:
0 1 2 3 4 5 4 3 2 1 0 1 2 3 4 5 4 etc
I have tried several different things, incrementing one number, modal operators. I could not figure this out, and I could not figure out correct search words.
So:
int offset = 0;
int number = 0;
while(true) {
offset++;
number = offset%5; // idea 1
number = (offset%5)-5 // idea 2
number = (offset/5)%5 // idea 3
number = 5 - (offset%5) // idea 4
}
None of those work, obviously. I get patterns like 0 1 2 3 4 5 0 1 2 3 4 5 or just continuous numbers.

Answer 1

I would wrap this in an if(offset % 10 <= 5) { ... } else { ... } and use your existing ideas.
Regardless you're going to want to work % 10 since that's how long your cycle is.

Answer 2

Hint These sequences are very closely related:
0 1 2 3 4 5 4 3 2 1 0 1 2 3 4 5 4 ...
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 ...

Answer 3

#include <iostream>
int main()
{
int i = 0;
bool plus = true;
while(true) {
std::cout << i << std::endl;
if (plus) i++; else i--;
if (i == 5 || i == 0) plus = !plus;
}
}

Answer 4

Is there a requirement to generate the numbers in a single statement with variables and operators?
If not, then use an bool variable which switches its value (true means increasing, false means decreasing) from true to false and vice versa.
i.e.
int start = 0 ;
bool which_way = true ;
int loop_times = 100 ;
while(--loop_times) {
std::cout << start ;
start += which_way ? 1 : -1 ;
if(start % 5 == 0)
which_way = !which_way ;
}

Answer 5

Here is a crazy way of outputting the number pong (with set limit)
#include <stdio.h>
int main()
{
bool bFlip = false; //Decides if number will increase or decrease
int nLimit = 5; //How far up the number will count.
//Start at 0, keep going as long as number never reaches past the limit
//And increase/decrease depending on bFlip
for(int nNum = 0; nNum <= nLimit; (bFlip ? nNum++ : nNum--))
{
printf("%d ", nNum);
//When number reaches either end, do a barrel roll!
if (nNum % nLimit == 0)
{
bFlip = !bFlip;
}
}
return 0;
}
Be warned that this loop will go on forever so if you are going to go with this approach then you will need to set a limit on how many numbers you want to display.

Answer 6

Yet another crack at generating the sequence you're after:
#include <iostream>
#include <list>
#include <iterator>
int main() {
std::list<int> nums = {{0, 1, 2, 3, 4, 5}};
auto begin = nums.begin();
auto iterator = nums.begin();
auto end = nums.end();
auto loop_times = 100;
while (--loop_times) {
while (iterator != end) {
std::cout << *iterator++;
}
iterator--;
while (iterator != begin) {
std::cout<< *--iterator;
}
iterator++;
}
}

Answer 7

Thanks for the tips. I got it working with a single statement.
int count = 0;
int num = 0;
int out = 0;
while (count++ < 100) {
cout << abs( (num%10) - 5 ) << endl;
num++;
}
// Output: 5 4 3 2 1 0 1 2 3 4 5 4 etc

Answer 8

I'd probably do something like this:
// If you want in the range -val to val
//#define PONG(val, i) (abs(val%(i*4)-i*2) - i)
// If you want the range 0 to val
#define PONG(val, i) (abs(val%(i*2)-i))
int main() {
for(int i = 0; i < 100; i++) {
cout << PONG(i, 5) << endl;
}
}
Prints:
5 4 3 2 1 0 1 2 3 4 5 4 3 2 1 0 1 2 ...