linked list stack get mentain minimum number

Linked list stack get mentain minimum number how to#
Linked list stack get mentain minimum number update#

prevMinEle is minEle before y was inserted

How previous minimum element, prevMinEle is, 2*minEle - y While popping out, if we find the element(y) less than the current minEle, we find the new minEle = 2*minEle – y. We can conclude 2*x - minEle < new minEle How 2*x - minEle is less than x in push()? The important thing to notes is, 2x – minEle will always be less than x (proved below), i.e., new minEle and while popping out this element we will see that something unusual has happened as the popped element is less than the minEle. When element to be inserted is less than minEle, we insert “2x – minEle”.

Number to be Inserted: 2, Stack is not empty, 2 minEle, original number is 5 and minEle is still 3.

Number to be Inserted: 5, Stack is not empty, 5> minEle, insert 5 into stack and minEle = 3.

Number to be Inserted: 3, Stack is empty, so insert 3 into stack and minEle = 3.

Actual minimum element is always stored in minEle.

Stack doesn’t hold actual value of an element if it is minimum so far.

Linked list stack get mentain minimum number update#

We remove 1 and update minEle as 2*2 – 1 = 3. For example, let the element to be removed be 1 and minEle be 2. This is where we retrieve previous minimum from current minimum and its value in stack. If y is less than minEle, the minimum element now becomes (2*minEle – y), so update (minEle = 2*minEle – y).If y is greater than or equal to minEle, the minimum element in the stack is still minEle.Pop() : Removes an element from top of stack. We update minEle as 2 and insert 2*2 – 3 = 1 into the stack.

If x is less than minEle, insert (2*x – minEle) into the stack and make minEle equal to x.

If x is greater than or equal to minEle, simply insert x.

If the stack is not empty, compare x with minEle.

If the stack is empty, insert x into the stack and make minEle equal to x.

Below are detailed steps and an explanation of work. To handle this, we push “2x – minEle” into the stack instead of x so that the previous minimum element can be retrieved using the current minEle and its value stored in the stack.

Linked list stack get mentain minimum number how to#

Now the interesting part is, how to handle the case when minimum element is removed. We define a variable minEle that stores the current minimum element in the stack. In this article, a new approach is discussed that supports minimum with O(1) extra space. Recommended PracticeGet minimum element from stackTry It!Īn approach that uses O(1) time and O(n) extra space is discussed here. ISRO CS Syllabus for Scientist/Engineer Exam.ISRO CS Original Papers and Official Keys.GATE CS Original Papers and Official Keys.