GATE2002-11

Question

The following recursive function in C is a solution to the Towers of Hanoi problem.

void move(int n, char A, char B, char C)  {
    if (......................) {
        move (.............................);
        printf("Move disk %d from pole %c to pole %c\n", n, A,C);
        move (.....................);
    }
}

Fill in the dotted parts of the solution.

Comments

If(n==1) { Printf("\n %s %c %s %c","move disk1 from pole",A,"to pole",B); Return; } Towers(n-1,A,C,B); Printf.... Towers(n-1,C,B,A);

Answer 1

void move(int n, char A, char B, char C) {
    if (n > 0) {
        move (n-1, A, C, B);
        printf("Move disk %d from pole %c to pole %c\n", n, A, C);
        move (n-1, B, A, C);
    } 
}

Comments

The snippet tells that A must be a source and C the destination.That means function would be move(src,spare,dest).

Firstcall(A,B,C) A to C using B intermediate

If we go by this defination, first move(n-1,A,C,B) will move n-1 disks to B using C as spare.

Now the 1 that remains is moved from A(src) to C(dest).

Shouldn't the last call then be move(n-1,B,A,C) ,that is moving the n-1 disk that were previously moved to intermediate node B over C(the destination) ?

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correct now?

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yes

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Yes it is correct !!

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need updation of this ans

https://gateoverflow.in/163078/tower-of-hanoi?state=comment-163092&show=163092#c163092

Answer 2

If(n==1) { Printf("\n %s %c %s %c","move disk1 from pole",A,"to pole",B); Return; } Towers(n-1,A,C,B); Printf.... Towers(n-1,C,B,A);