Min Stack Min Change Count

Problem

Simulate a stack with O(1) minimum tracking. operations contains "push", "pop", or "get_min"; values supplies the pushed value and is ignored otherwise. Return [min_change_count, results] where min_change_count counts pushes that set a new strict minimum (the first push counts) and results collects each get_min value (None when the stack is empty).

Hint

Keep a parallel minimum stack: each entry is the minimum of everything pushed so far.

Test cases

case 1

in: [["push","push","get_min","push","get_min","pop","get_min"],[3,5,0,2,0,0,0]]

expected: [2,[3,2,3]]

case 2

in: [["push","push","get_min","pop","get_min","pop","get_min"],[1,1,0,0,0,0,0]]

expected: [1,[1,1,null]]

case 3

in: [[],[]]

expected: [0,[]]

case 4

in: [["get_min","pop"],[0,0]]

expected: [0,[null]]

Starter codePython

def min_stack_changes(operations, values):
    # Your code here
    pass

4 test cases · run your code against them in the editor