"Coding Interview Guide" - the effectiveness and the effective length of the longest character string in brackets

[ Title ]

　　Given a string str, the overall judgment is not a valid string brackets

　　For example, str = "()", returns true; str = "(() ())", returns true; str = "(())", returns true;

   　　　　str = "())", return false; str = "() (", return false; str = "() a ()", return false;

my：

 1     import java.util.Stack;
 2 
 3     public boolean my_isValid(String str)
 4     {
 5         if(str == null || str.equals(""))
 6         {
 7             return false;
 8         }
 9 
10         char[] cstr = str.toCharArray();
11         Stack<Character> stack = new Stack<>();
12         for(char c : cstr)
13         {
14             if(c == '(')
15             {    
16                 stack.push(c);
17             }
18             else if(c == ')')
19             {
20                 if(stack.empty())
21                 {
22                     return false;
23                 }
24                 stack.pop();
25             }
26             else
27             {
28                 return false;
29             }
30         }
31         return stack.empty() ? true : false;
32     }

Time complexity: O (N), the spatial complexity: O (N)

 

Left Teacher:

. 1      public  Boolean isValid (String STR)
 2      {
 . 3          IF (STR == null || str.equals ( "" ))
 . 4          {
 . 5              return  to false ;
 . 6          }
 . 7  
. 8          char [] = Chas str.toCharArray ();
 . 9          int 0 = COUNT;      // simply set a counter 
10          for ( char C: Chas)
 . 11          {
 12 is              IF (= C '(' && = C ')'!! )
 13 is              {
 14                  return false;
15             }
16             if(c == ')' && --count < 0)
17             {
18                 return false;
19             }
20             if(c == '(')
21             {
22                 count++;
23             }
24         }
25 
26         return count == 0;
27     }

Time complexity: O (N), the spatial complexity: O (1)

 

[Advanced] title

　　Given a bracket string str, returns the longest substring effective brackets

　　For example, str = "(() ())", returns 6; str = "())", return to 2; str = "() (() () (", returns 4

 

 

 

Source: Left Cheng Yun teacher "Programmer Code Interview Guide"