title: Minimum Number Of Bracket Reversals Needed To Make An Expression Balanced
signature: class Solution {
  
      public Integer minimumNumberOfBracketReversalsNeededToMakeAnExpressionBalanced(String expr) {
test_code: import static java.util.Map.entry;  
  import java.util.*;
  import java.lang.*;
  // TESTING CODE 
  // ============================================
  class QuestionEvaluator {
      public static String validateSolution(String expr, Integer expected){
          try{
              Driver driver = new Driver();
              if (driver.run(expr,expected)){
                  return "PASSED";
              }
              return "FAILED";
              
          } catch (Exception exception_obj){
              return exception_obj.getClass().getSimpleName();
          }
  
      }
      public static void main(String[] args) {
          String result;
          result = validateSolution("}{", 1);
          System.out.println(String.format("%s%s","TEST-0...",result));    
      
          result = validateSolution("{{{", -1);
          System.out.println(String.format("%s%s","TEST-1...",result));    
      
          result = validateSolution("{{{{", 2);
          System.out.println(String.format("%s%s","TEST-2...",result));    
      
          result = validateSolution("{{{{}}", 3);
          System.out.println(String.format("%s%s","TEST-3...",result));    
      
          result = validateSolution("}{{}}{{{", 4);
          System.out.println(String.format("%s%s","TEST-4...",result));    
      
          result = validateSolution("{}", 1);
          System.out.println(String.format("%s%s","TEST-5...",result));    
      
          result = validateSolution("", 0);
          System.out.println(String.format("%s%s","TEST-6...",result));    
      
          result = validateSolution("8", -1);
          System.out.println(String.format("%s%s","TEST-7...",result));    
      
          result = validateSolution("01111000", 4);
          System.out.println(String.format("%s%s","TEST-8...",result));    
      
          result = validateSolution("XPkERzHcpId", -1);
          System.out.println(String.format("%s%s","TEST-9...",result));    
      
      }
  }
  
  class Driver{
      public boolean run(String expr, Integer expected){
  
          PLACEHOLDER_CLS_NAME sol = new PLACEHOLDER_CLS_NAME();
          return validateSolution(sol.PLACEHOLDER_FN_NAME(expr),expected);
      }
      
      public boolean validateSolution(Integer actual, Integer expected){
          return actual.equals(expected);
      }
  }
  
  
  // SOLUTION CODE
  // ============================================
  PLACEHOLDER_CODE_BODY
source_py: def minimum_number_of_bracket_reversals_needed_to_make_an_expression_balanced(expr):
      lenn = len(expr)
      if (lenn % 2):
          return (- 1)
      s = []
      for i in range(lenn):
          if ((expr[i] == '') and len(s)):
              if (s[0] == ''):
                  s.pop(0)
              else:
                  s.insert(0, expr[i])
          else:
              s.insert(0, expr[i])
      red_len = len(s)
      n = 0
      while (len(s) and (s[0] == '')):
          s.pop(0)
          n += 1
      return ((red_len // 2) + (n % 2))
source_cpp: int minimum_number_of_bracket_reversals_needed_to_make_an_expression_balanced(string expr) {
    int len = expr . length ( );
    if ( len % 2 ) return - 1;
    stack < char > s;
    for ( int i = 0;
    i < len;
    i ++ ) {
      if ( expr [ i ] == '}' && ! s . empty ( ) ) {
        if ( s . top ( ) == '{' ) s . pop ( );
        else s . push ( expr [ i ] );
      }
      else s . push ( expr [ i ] );
    }
    int red_len = s . size ( );
    int n = 0;
    while ( ! s . empty ( ) && s . top ( ) == '{' ) {
      s . pop ( );
      n ++;
    }
    return ( red_len / 2 + n % 2 );
  }