Whats the logic to print the truth table values given the x in 2^x?

Question

given

x=2 rows= pow(2,2)=4 and colums=2

output:

T T
T F
F T
F F

x=3 rows= pow(2,3)=8 and colums=8

output:

T T T
T T F
T F T
T F F
F T T
F T F
F F T
F F F

and so on. it could be to print like this or to create an char array with 2^x rows and x columns and with T/F as values.

I can think of it as for say column number j - change should occur after pow(2,x-(j+1))

thanks; pseudo code or java is preferred

yes I hv tried something - as I said in post ..in each columns change occurs after pow(2,x-(j+1)) so if x=3 for colums 0 -after 4 rows and column 1 after 2 and for colums 3 its after 1. — Nikhil, Jul 18 '14 at 11:38
i can think of using recursive function..but I am not sure whether it would work if i need to put this in array.. — Nikhil, Jul 18 '14 at 11:40
Change T to 0 and F to 1 and you've got incrementing binary digits — Revive, Jul 18 '14 at 11:40
Searching "generate all truth tables" in the box up top yielded http://stackoverflow.com/q/22202822/2336725 http://stackoverflow.com/q/4221258/2336725 and http://stackoverflow.com/q/3504642/2336725 — Teepeemm, Jul 18 '14 at 14:12

score 2 · Answer 1 · 2014-07-18T15:12:48.240

2

Recursively: take the table for N-1 and prepend T to all lines, then repeat with F, and you get the table for N.

void Print(String Line, int N) {
  if (N== 0) println(Line); else { Print("T " + Line, N-1); Print("F " + Line, N-1); }
}

...
Print("", 5);
....

edited Jul 18 '14 at 15:12

answered Jul 18 '14 at 13:52

Explain what you're doing and why you're doing it. – stealthjong Jul 18 '14 at 14:49

score 1 · Accepted Answer · answered Jul 18 '14 at 11:40

I think it may helps you :

public static void main(String args[]) {
        int size = 2;      // change the size ans get your truth table.
        generateTable(0, size, new int[size]);
    }

    private static void generateTable(int index, int size, int[] current) {
        if (index == size) {
            for (int i = 0; i < size; i++) {
                System.out.print(current[i] + " ");
            }
            System.out.println();
        } else {
            for (int i = 0; i < 2; i++) {
                current[index] = i;
                generateTable(index + 1, size, current);
            }
        }
    }

Output(when pass the size = 2) :

score 1 · Answer 3 · answered Jul 18 '14 at 11:45

1

How about:

for(double x=Math.pow(2,col-1); x<Math.pow(2,col); x++)
    System.out.println(Integer.toBinaryString((int)x));
}

Just set col to how many columns you want outputted

answered Jul 18 '14 at 11:45

Revive

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Whats the logic to print the truth table values given the x in 2^x?

3 Answers3