leetcode_gym/_problems/minStack.md

layout, title, last_solved, category, leetcode_url, status

layout	title	last_solved	category	leetcode_url	status
page	Tempalte				Attempted

Problem

Design a stack that supports push, pop, top, and retrieving the minimum element in constant time.

push(x) -- Push element x onto stack.
pop() -- Removes the element on top of the stack.
top() -- Get the top element.
getMin() -- Retrieve the minimum element in the stack.
 

Example 1:

Input
["MinStack","push","push","push","getMin","pop","top","getMin"]
[[],[-2],[0],[-3],[],[],[],[]]

Output
[null,null,null,null,-3,null,0,-2]

Explanation
MinStack minStack = new MinStack();
minStack.push(-2);
minStack.push(0);
minStack.push(-3);
minStack.getMin(); // return -3
minStack.pop();
minStack.top();    // return 0
minStack.getMin(); // return -2

Solution

{% highlight python %}

class MinStack:

def __init__(self):

    self.stack = []
    

def push(self, x: int) -> None:
    
    if not self.stack:
        minSoFar = x
    else:
        
        prevMin = self.stack[-1][1]
        minSoFar = min(prevMin, x)
        
    item = (x, minSoFar)
    self.stack.append( item )
    

def pop(self) -> None:
    
    if self.stack:
        item = self.stack.pop()
        return item[0]
    

def top(self) -> int:
    
    if self.stack:
        item = self.stack[-1]
        return item[0]

def getMin(self) -> int:
    
    if self.stack:
        item = self.stack[-1]
        return item[1]

{% endhighlight %}

---

{% highlight python %}

{% endhighlight %}