# Tower of Hanoi Iterative C

## tower.txt

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WAP in C to implement iterative Towers of Hanoi. PPL Practical Question Btech IPU Syllabus.

``````// C Program for Iterative Tower of Hanoi
#include <stdio.h>
#include <math.h>
#include <stdlib.h>
#include <limits.h>

// A structure to represent a stack
struct Stack
{
unsigned capacity;
int top;
int *array;
};

// function to create a stack of given capacity.
struct Stack* createStack(unsigned capacity)
{
struct Stack* stack =
(struct Stack*) malloc(sizeof(struct Stack));
stack -> capacity = capacity;
stack -> top = -1;
stack -> array =
(int*) malloc(stack -> capacity * sizeof(int));
return stack;
}

// Stack is full when top is equal to the last index
int isFull(struct Stack* stack)
{
return (stack->top == stack->capacity - 1);
}

// Stack is empty when top is equal to -1
int isEmpty(struct Stack* stack)
{
return (stack->top == -1);
}

// Function to add an item to stack. It increases
// top by 1
void push(struct Stack *stack, int item)
{
if (isFull(stack))
return;
stack -> array[++stack -> top] = item;
}

// Function to remove an item from stack. It
// decreases top by 1
int pop(struct Stack* stack)
{
if (isEmpty(stack))
return INT_MIN;
return stack -> array[stack -> top--];
}

//Function to show the movement of disks
void moveDisk(char fromPeg, char toPeg, int disk)
{
printf("Move the disk %d from \'%c\' to \'%c\'\n",
disk, fromPeg, toPeg);
}

// Function to implement legal movement between
// two poles
void moveDisksBetweenTwoPoles(struct Stack *src,
struct Stack *dest, char s, char d)
{
int pole1TopDisk = pop(src);
int pole2TopDisk = pop(dest);

// When pole 1 is empty
if (pole1TopDisk == INT_MIN)
{
push(src, pole2TopDisk);
moveDisk(d, s, pole2TopDisk);
}

// When pole2 pole is empty
else if (pole2TopDisk == INT_MIN)
{
push(dest, pole1TopDisk);
moveDisk(s, d, pole1TopDisk);
}

// When top disk of pole1 > top disk of pole2
else if (pole1TopDisk > pole2TopDisk)
{
push(src, pole1TopDisk);
push(src, pole2TopDisk);
moveDisk(d, s, pole2TopDisk);
}

// When top disk of pole1 < top disk of pole2
else
{
push(dest, pole2TopDisk);
push(dest, pole1TopDisk);
moveDisk(s, d, pole1TopDisk);
}
}

//Function to implement TOH puzzle
void tohIterative(int num_of_disks, struct Stack
*src, struct Stack *aux,
struct Stack *dest)
{
int i, total_num_of_moves;
char s = 'S', d = 'D', a = 'A';

//If number of disks is even, then interchange
//destination pole and auxiliary pole
if (num_of_disks % 2 == 0)
{
char temp = d;
d = a;
a = temp;
}
total_num_of_moves = pow(2, num_of_disks) - 1;

//Larger disks will be pushed first
for (i = num_of_disks; i >= 1; i--)
push(src, i);

for (i = 1; i <= total_num_of_moves; i++)
{
if (i % 3 == 1)
moveDisksBetweenTwoPoles(src, dest, s, d);

else if (i % 3 == 2)
moveDisksBetweenTwoPoles(src, aux, s, a);

else if (i % 3 == 0)
moveDisksBetweenTwoPoles(aux, dest, a, d);
}
}

// Driver Program
int main()
{
// Input: number of disks
unsigned num_of_disks = 3;

struct Stack *src, *dest, *aux;

// Create three stacks of size 'num_of_disks'
// to hold the disks
src = createStack(num_of_disks);
aux = createStack(num_of_disks);
dest = createStack(num_of_disks);

tohIterative(num_of_disks, src, aux, dest);
return 0;
}

``````

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Last Updated: July 17, 2022