from stack import MainStack


class MinStack:
    # Initializing min and main stack
    def __init__(self):
        self.min_stack = MainStack()
        self.main_stack = MainStack()

    # Pop() removes and returns value from min_stack
    def pop(self):
        self.min_stack.pop()
        # Returns the popped value from main_stack
        return self.main_stack.pop()

    # Pushes values into min_stack
    def push(self, value):
        self.main_stack.push(value)

        # If the min_stack is empty, or the value being pushed is less than
        # the minimum (top) value of min_stack
        if self.min_stack.is_empty() or value < self.min_stack.top():
            # Push this new value to the min_stack
            self.min_stack.push(value)
        else:
            # Keep the minimum value at the top of min_stack
            self.min_stack.push(self.min_stack.top())

    # Returns minimum value from min_stack in O(1) Time
    def min_number(self):
        if self.min_stack.is_empty():
            return None
        else:
            return self.min_stack.top()


# driver code
def main():

    # list of push and pop commands as input
    input_stacks = [
                   [[9, 3, 1, 4, 2, 5], [1, 1, 0, 1, 0, 1]],
                   [[5, 10, 6, 23, 2], [1, 1, 0, 1, 0]],
                   [[1, 2, 3, 4, 5, 6, -3, -8], [1, 1, 0, 1, 0, 1, 1, 0]],
                   [[14, 32, 66, 71, 22, 50, 35], [1, 0, 1, 1, 0, 1, 0]],
                   [[-2, 4, 5, 0, 1, -3], [1, 1, 1, 1, 1, 1]]
    ]

    # loop over all the input streams
    for i in range(len(input_stacks)):
        print(i + 1, ".\t Starting operations:", sep="")

        # initialize a Min Stack
        min_stack_obj = MinStack()

        # loop over all the commands
        for j in range(len(input_stacks[i][1])):

            # 1 denotes push, 0 denotes pop
            if input_stacks[i][1][j] == 1:
                if input_stacks[i][0] == []:
                    next
                else:
                    print("\t\t Push(", input_stacks[i][0][j], ")", sep="")
                    min_stack_obj.push(input_stacks[i][0][j])
            else:
                print("\t\t Pop() returns ", min_stack_obj.pop(), sep="")
        print("\t Minimum number in the stack is: ",
              min_stack_obj.min_number(), sep="")
        print("-" * 100)


if __name__ == '__main__':
    main()