title: Minimum Number Of Bracket Reversals Needed To Make An Expression Balanced
signature: pub fn minimum_number_of_bracket_reversals_needed_to_make_an_expression_balanced(expr: String) -> i32 {
test_code: use std::collections::HashMap;
  use std::collections::HashSet;
  use std::cmp::*;
  use std::collections::*;
  use std::fmt::*; 
  
  
  // SOLUTION CODE
  // ============================================
  PLACEHOLDER_CODE_BODY
  
  // TESTING CODE 
  // ============================================
  pub fn validate_solution(actual: i32, expected: i32)->bool{
  return actual==expected
  }
  pub fn driver(expr: String, expected: i32)->String{
      if validate_solution(PLACEHOLDER_FN_NAME(expr), expected) {
        return "PASSED".to_string();
      };
      return "FAILED".to_string();
  
  }
  
  fn main() {
      println!("TEST-0...{}", driver(
        "}{".to_string(), 
        1
      ));
      
      println!("TEST-1...{}", driver(
        "{{{".to_string(), 
        -1
      ));
      
      println!("TEST-2...{}", driver(
        "{{{{".to_string(), 
        2
      ));
      
      println!("TEST-3...{}", driver(
        "{{{{}}".to_string(), 
        3
      ));
      
      println!("TEST-4...{}", driver(
        "}{{}}{{{".to_string(), 
        4
      ));
      
      println!("TEST-5...{}", driver(
        "{}".to_string(), 
        1
      ));
      
      println!("TEST-6...{}", driver(
        "".to_string(), 
        0
      ));
      
      println!("TEST-7...{}", driver(
        "8".to_string(), 
        -1
      ));
      
      println!("TEST-8...{}", driver(
        "01111000".to_string(), 
        4
      ));
      
      println!("TEST-9...{}", driver(
        "XPkERzHcpId".to_string(), 
        -1
      ));
      
  }
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 );
  }