Minimum Element in Stack in O(1) Space

Hard

Problem Statement

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

Examples

1Example 1

Input:

{
  "operations": [
    "push",
    "push",
    "push",
    "getMin",
    "pop",
    "top",
    "getMin"
  ],
  "values": [
    -2,
    0,
    -3
  ]
}

Output:

[
  -3,
  0,
  -2
]

2Example 2

Input:

{
  "operations": [
    "push",
    "getMin",
    "pop",
    "getMin"
  ],
  "values": [
    0
  ]
}

Output:

[
  0,
  -1
]

3Example 3

Input:

{
  "operations": [
    "push",
    "push",
    "getMin",
    "push",
    "getMin"
  ],
  "values": [
    2147483646,
    2147483646,
    2147483647
  ]
}

Output:

[
  2147483646,
  2147483646
]