Cesarion - 10 months ago 82

Java Question

I wonder how to convert a recursive function/class to an iterative one.

I have made a recursive Pascal's triangle, and now need to compare it to an iterative.

`public class RecursivePascal extends ErrorPascal implements Pascal`

{

private int n;

RecursivePascal(int n) throws Exception

{

super(n);

this.n = n;

}

public void printPascal()

{

printPascal(n, false);

}

public void printPascal(boolean upsideDown)

{

printPascal(n, upsideDown);

}

private void printPascal(int n, boolean upsideDown)

{

if (n == 0) { return; }

if (!upsideDown) { printPascal(n - 1, upsideDown); }

for (int i = 0; i < n; i++)

{

System.out.print(binom(n - 1, i) + (n == i + 1 ? "\n" : " "));

}

if (upsideDown) { printPascal(n - 1, upsideDown); }

}

public int binom(int n, int k)

{

if (k == 0 || n == k) { return 1; }

return binom(n - 1, k - 1) + binom(n - 1, k);

}

}

What do I need to change in order to make it iterative? I'm still a little unsure of how this works. Thanks in advance!

Answer Source

Plug these two functions below into a pascal class. I tested it and it works. That link that Prateek Darmwal posted is pretty much the same thing.

```
public void nonRecursivePrint()
{
nonRecursivePrint(n, true);
}
public void nonRecursivePrint(int n, boolean upsideDown)
{
if (!upsideDown)
{
for (int j=0; j<(n+1); j++)
{
for (int i=0; i<(j); i++)
{
System.out.print(binom(j - 1, i) + (j == i + 1 ? "\n" : " "));
}
}
}
else
{
for (int j=n; j>0; j--)
{
for (int i=0; i<(j); i++)
{
System.out.print(binom(j - 1, i) + (j == i + 1 ? "\n" : " "));
}
}
}
}
```