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Find maximum depth of nested parenthesis in a string

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  • Difficulty Level : Medium
  • Last Updated : 24 Jun, 2022
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We are given a string having parenthesis like below 
     “( ((X)) (((Y))) )” 
We need to find the maximum depth of balanced parenthesis, like 4 in the above example. Since ‘Y’ is surrounded by 4 balanced parentheses. 
If parenthesis is unbalanced then return -1. 

Examples : 

Input : S = "( a(b) (c) (d(e(f)g)h) I (j(k)l)m)";
Output : 4

Input : S = "( p((q)) ((s)t) )";
Output : 3

Input : S = "";
Output : 0

Input : S = "b) (c) ()";
Output : -1 

Input : S = "(b) ((c) ()"
Output : -1 

Method 1 (Uses Stack):

A simple solution is to use a stack that keeps track of current open brackets. 

  1. Create a stack. 
  2. Traverse the string, do following for every character
    • If current character is ‘(’ push it to the stack .
    • If character is ‘)’, pop an element.
    • Maintain maximum count during the traversal. 

Below is the code implementation of the algorithm.

C++




// A C++ program to find the maximum depth of nested
// parenthesis in a given expression
#include <bits/stdc++.h>
using namespace std;
 
int maxDepth(string& s)
{
    int count = 0;
    stack<int> st;
 
    for (int i = 0; i < s.size(); i++) {
        if (s[i] == '(')
            st.push(i); // pushing the bracket in the stack
        else if (s[i] == ')') {
            if (count < st.size())
                count = st.size();
            /*keeping track of the parenthesis and storing
            it before removing it when it gets balanced*/
            st.pop();
        }
    }
    return count;
}
 
// Driver program
int main()
{
    string s = "( ((X)) (((Y))) )";
    cout << maxDepth(s);
 
    // This code is contributed by rakeshsahni
 
    return 0;
}


Java




/*package whatever //do not write package name here */
 
import java.io.*;
import java.util.*;
class GFG {
    public static int maxDepth(String s) {
        int count=0;
        Stack<Integer> st = new Stack<>();
         
        for(int i=0;i<s.length();i++)
        {
            if(s.charAt(i) == '(')
                st.push(i);//pushing the bracket in the stack
            else if(s.charAt(i) == ')')
            {
                if(count < st.size())
                    count = st.size();
              /*keeping track of the parenthesis and storing it before removing
              it when it gets balanced*/
                st.pop();
            }
        }
        return count;
}
    public static void main (String[] args) {
        System.out.println(maxDepth("( ((X)) (((Y))) )"));
    }
}


Python3




# Python code to implement the approach
 
 
def maxDepth(s):
 
    count = 0
    st = []
 
    for i in range(len(s)):
        if (s[i] == '('):
            st.append(i) # pushing the bracket in the stack
        elif (s[i] == ')'):
            if (count < len(st)):
                count = len(st)
            # keeping track of the parenthesis and storing
            # it before removing it when it gets balanced
            st.pop()
         
    return count
 
# Driver program
 
s = "( ((X)) (((Y))) )"
print(maxDepth(s))
 
 
# This code is contributed by shinjanpatra


C#




//C# program to find the  maximum depth
//of nested parenthesis in a string
using System;
using System.Collections;
 
public class GFG{
     
    static int maxDepth(string s){
        int count=0;
        Stack st = new Stack();
          
        for(int i=0;i<s.Length;i++)
        {
             
            if(s[i]=='('){
                st.Push(i);//pushing the bracket in the stack
            }else{
                if(s[i]==')'){
                    if(count<st.Count){
                         
                        count=st.Count;
                    }
                    /*keeping track of the parenthesis and storing it before removing
                    it when it gets balanced*/
                    st.Pop();
                }
            }
             
        }
        return count;
    }
     
    //Driver Code
    static public void Main (){
        Console.Write(maxDepth("( ((X)) (((Y))) )"));//Function call
    }
}
 
//This code is contributed by shruti456rawal


Javascript




<script>
 
// JavaScript code to implement the approach
 
function maxDepth(s){
 
    let count = 0
    let st = []
 
    for(let i=0;i<s.length;i++){
        if (s[i] == '(')
            st.push(i) // pushing the bracket in the stack
        else if (s[i] == ')'){
            if (count < st.length)
                count = st.length
            // keeping track of the parenthesis and storing
            // it before removing it when it gets balanced
            st.pop()
        }
    }
         
    return count
}
 
// Driver program
 
let s = "( ((X)) (((Y))) )"
document.write(maxDepth(s),"</br>")
 
 
// This code is contributed by shinjanpatra
 
</script>


Output

4

Time Complexity: O(N) where n is number of elements in given string. As, we are using a loop to traverse N times so it will cost us O(N) time 
Auxiliary Space: O(1), as we are using extra space for stack.

Method 2 ( O(1) auxiliary space ):

This can also be done without using stack.  

  1. 1) Take two variables max and current_max, initialize both of them as 0.
  2. 2) Traverse the string, do following for every character
    • If current character is ‘(’, increment current_max and  update max value if required.
    • If character is ‘)’. Check if current_max is positive or not (this condition ensure that parenthesis are balanced). 
      If positive that means we previously had a ‘(’ character 
      so decrement current_max without worry. 
      If not positive then the parenthesis are not balanced. 
      Thus return -1. 
  3. If current_max is not 0, then return -1 to ensure that the parenthesis
    are balanced. Else return max

Below is the implementation of the above algorithm.

C++




// A C++ program to find the maximum depth of nested
// parenthesis in a given expression
#include <iostream>
using namespace std;
 
// function takes a string and returns the
// maximum depth nested parenthesis
int maxDepth(string S)
{
    int current_max = 0; // current count
    int max = 0; // overall maximum count
    int n = S.length();
 
    // Traverse the input string
    for (int i = 0; i < n; i++)
    {
        if (S[i] == '(')
        {
            current_max++;
 
            // update max if required
            if (current_max > max)
                max = current_max;
        }
        else if (S[i] == ')')
        {
            if (current_max > 0)
                current_max--;
            else
                return -1;
        }
    }
 
    // finally check for unbalanced string
    if (current_max != 0)
        return -1;
 
    return max;
}
 
// Driver program
int main()
{
    string s = "( ((X)) (((Y))) )";
    cout << maxDepth(s);
    return 0;
}


Java




//Java program to find the maximum depth of nested
// parenthesis in a given expression
 
class GFG {
// function takes a string and returns the
// maximum depth nested parenthesis
 
    static int maxDepth(String S) {
        int current_max = 0; // current count
        int max = 0; // overall maximum count
        int n = S.length();
 
        // Traverse the input string
        for (int i = 0; i < n; i++) {
            if (S.charAt(i) == '(') {
                current_max++;
 
                // update max if required
                if (current_max > max) {
                    max = current_max;
                }
            } else if (S.charAt(i) == ')') {
                if (current_max > 0) {
                    current_max--;
                } else {
                    return -1;
                }
            }
        }
 
        // finally check for unbalanced string
        if (current_max != 0) {
            return -1;
        }
 
        return max;
    }
 
// Driver program
    public static void main(String[] args) {
        String s = "( ((X)) (((Y))) )";
        System.out.println(maxDepth(s));
    }
}


Python3




# A Python program to find the maximum depth of nested
# parenthesis in a given expression
 
# function takes a string and returns the
# maximum depth nested parenthesis
def maxDepth(S):
    current_max = 0
    max = 0
    n = len(S)
 
    # Traverse the input string
    for i in range(n):
        if S[i] == '(':
            current_max += 1
 
            if current_max > max:
                max = current_max
        else if S[i] == ')':
            if current_max > 0:
                current_max -= 1
            else:
                return -1
 
    # finally check for unbalanced string
    if current_max != 0:
        return -1
 
    return max
 
# Driver program
s = "( ((X)) (((Y))) )"
print (maxDepth(s))
 
# This code is contributed by BHAVYA JAIN


C#




// C# program to find the
// maximum depth of nested
// parenthesis in a given expression
using System;
class GFG {
   
// function takes a string
// and returns the maximum
// depth nested parenthesis
 
static int maxDepth(string S)
{
  // current count
  int current_max = 0;
   
  // overall maximum count
  int max = 0;
   
  int n = S.Length;
 
  // Traverse the input string
  for (int i = 0; i < n; i++)
  {
    if (S[i] == '(')
    {
      current_max++;
 
      // update max if required
      if (current_max > max)
      {
        max = current_max;
      }
    }
    else if (S[i] == ')')
    {
      if (current_max > 0)
      {
        current_max--;
      }
      else
      {
        return -1;
      }
    }
  }
 
  // finally check for unbalanced string
  if (current_max != 0)
  {
    return -1;
  }
 
  return max;
}
 
// Driver program
public static void Main()
{
  string s = "(((X)) (((Y))))";
  Console.Write(maxDepth(s));
}
}
 
// This code is contributed by Chitranayal


PHP




<?php
// A PHP program to find the
// maximum depth of nested
// parenthesis in a given
// expression
 
// function takes a string 
// and returns the maximum
// depth nested parenthesis
function maxDepth($S)
{
    // current count
    $current_max = 0;
     
    // overall maximum count
    $max = 0;
    $n = strlen($S);
 
    // Traverse the input string
    for ($i = 0; $i < $n; $i++)
    {
        if ($S[$i] == '(')
        {
            $current_max++;
 
            // update max if required
            if ($current_max> $max)
                $max = $current_max;
        }
         
        else if ($S[$i] == ')')
        {
            if ($current_max>0)
                $current_max--;
            else
                return -1;
        }
    }
 
    // finally check for
    // unbalanced string
    if ($current_max != 0)
        return -1;
 
    return $max;
}
 
// Driver Code
$s = "( ((X)) (((Y))) )";
echo maxDepth($s);
 
// This code is contributed by mits
?>


Javascript




<script>
 
// Javascript program to find the
// maximum depth of nested parenthesis
// in a given expression
 
// Function takes a string and returns the
// maximum depth nested parenthesis
function maxDepth(S)
{
     
    // Current count
    let current_max = 0;
     
    // Overall maximum count
    let max = 0;
    let n = S.length;
     
    // Traverse the input string    
    for(let i = 0; i < n; i++)
    {
        if (S[i] == '(')
        {
            current_max++;
             
            // Update max if required
            if (current_max > max)
            {
                max = current_max;
            }
        }
        else if (S[i] == ')')
        {
             if (current_max > 0)
             {
                current_max--;
            } else
            {
                return -1;
            }
        }
    }
     
    // Finally check for unbalanced string
    if (current_max != 0)
    {
        return -1;
    }
 
    return max;
}
 
// Driver code
let s = "( ((X)) (((Y))) )";
 
document.write(maxDepth(s));
 
// This code is contributed by avanitrachhadiya2155
     
</script>


Output

4

Time Complexity: O(n) where n is number of elements in given string. As, we are using a loop to traverse N times so it will cost us O(N) time.
Auxiliary Space: O(1), as we are not using any extra space.


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