*879*

Question: You are given a stack and you have to reverse it, using only stack operations push and pop.

The algorithm for the above problem can be given in this way:-

- First POP all elements of the stack till it becomes empty
- Now for each upward step in the recursion, push the elements at the bottom of the stack.

void reverseStack(struct stackNode * top) { int data; if(isStackEmpty(top)) return; //get the top data data = POP(top); //recursive call for the next top element reverseStack(top); //after the recursion ends, we need to insert the numbers at the Bottom insertAtBottom(top, data); } void insertAtBottom(struct stackNode * top, int data) { int temp; //check for terminating condition of recursive call if(isStackEmpty(top)) { //when the stack is empty, just add the data //this will be the last data of original stack top = push(top,data); return; } //again we get the top elements one by one temp = POP(top); //a recursive call insertAtBottom(top, data); top = push(top, temp); }