# Given a string of brackets, return the count of brackets that are properly matched

A string of brackets is considered correctly matched if every opening bracket in the string can be paired up with a later closing bracket, and vice versa. For instance, “(())()” is correctly matched, whereas “)(“ and “((” aren’t. For instance, “((” could become correctly matched by adding two closing brackets at the end, so you’d return 2.

Given a string that consists of brackets, write a function bracketMatch that takes a bracket string as an input and returns the minimum number of brackets you’d need to add to the input in order to make it correctly matched.

My approach:

 import java.io.*;
import java.util.*;

class Solution {

static int bracketMatch(String text) {
//Maintain 2 variables
int ob = 0;//ob
int cb = 0;//cb
int wb= 0;//wb

for( int i = 0; i < text.length(); i++ )
{
//Check for openBracket
if( text.charAt(i) == '(')
ob++;

//Check for closeBracket
if( text.charAt(i) == ')')
cb++;

//Check if closeBracketct > openBracketct
if( cb > ob )
{
wb++;
ob = 0;
cb = 0;
}
}
return (wb + (ob - cb));
}

public static void main(String[] args) {
//System.out.println(bracketMatch("())("));
//System.out.println(bracketMatch("(((())))"));
System.out.println(bracketMatch("(((())"));
//  System.out.println(bracketMatch("))))"));
}

}


I have a few questions regarding the above code:

1) How can I further optimize this code?

2) Am I using too many variables?

3) Is there a better approach than mine?

Reference

• You need to use a stack. This question is from cracking the coding interview Feb 4, 2018 at 5:33
• Thanks. Any other solution where I can reduce the number of variables required? Feb 4, 2018 at 5:41
• You may find the filter part of this answer useful, basicly you keep a stack, and make sure that when you see a closing bracket you have already seen an opening bracket to match it Feb 4, 2018 at 22:15

We dont need close variable if we can decrease open by 1 when close bracket is found.

public class MatchBrackets{

public static int matchBrackets(String brackets){

int open = 0;
int count =0;

for(int i=0;i<brackets.length();i++){
if(brackets.charAt(i)=='('){
open++;
}else if(brackets.charAt(i)==')'){
open--;
}
if(open<0){
count++;
open++;
}
}
return count+open;
}

public static void main(String[] args) {

System.out.println(matchBrackets("())("));
System.out.println(matchBrackets("(((())))"));
System.out.println(matchBrackets("))))"));
}}