# [Leet Code] Maximum Nesting Depth of the Parentheses

LeetCode: https://leetcode.com/problems/maximum-nesting-depth-of-the-parentheses/

Problem:

A string is a **valid parentheses string** (denoted **VPS**) if it meets one of the following:

- It is an empty string
`""`

, or a single character not equal to`"("`

or`")"`

, - It can be written as
`AB`

(`A`

concatenated with`B`

), where`A`

and`B`

are**VPS**'s, or - It can be written as
`(A)`

, where`A`

is a**VPS**.

We can similarly define the **nesting depth** `depth(S)`

of any VPS `S`

as follows:

`depth("") = 0`

`depth(C) = 0`

, where`C`

is a string with a single character not equal to`"("`

or`")"`

.`depth(A + B) = max(depth(A), depth(B))`

, where`A`

and`B`

are**VPS**'s.`depth("(" + A + ")") = 1 + depth(A)`

, where`A`

is a**VPS**.

For example, `""`

, `"()()"`

, and `"()(()())"`

are **VPS**'s (with nesting depths 0, 1, and 2), and `")("`

and `"(()"`

are not **VPS**'s.

Given a **VPS** represented as string `s`

, return *the **nesting depth** of *`s`

.

**Example 1:**

**Input:** s = "(1+(2*3)+((8)/4))+1"

**Output:** 3

**Explanation:** Digit 8 is inside of 3 nested parentheses in the string.

**Example 2:**

**Input:** s = "(1)+((2))+(((3)))"

**Output:** 3

**Example 3:**

**Input:** s = "1+(2*3)/(2-1)"

**Output:** 1

**Example 4:**

**Input:** s = "1"

**Output:** 0

Solution:

`class Solution(object):`

def maxDepth(self, s):

"""

:type s: str

:rtype: int

"""

stack = []

max_val = 0

for i in s:

if i == "(":

stack.append(i)

if i == ")":

stack.pop()

length = len(stack)

if length > max_val:

max_val = length

return max_val

Explanation:

For this problem, we want to create a stack that will hold the amount of `"("`

we have in our string. If we encounter a `"("`

we will append it to the stack, otherwise, we will pop it. This will mean that outermost parenthesis will persist if we have something like `"(a(b) + cd(e))`

the `(b)`

will be removed but it will also increase our stack length, and therefore add to our max val!