Odtnhj

How can you check whether a specific char comes before another char using a for-loop?

E.g. the function should return false if ')' comes before '('. So the following strings would be false: ')abc', 'a)abc(', ')abc'

Lets define a function to resolve your problem

Note that below solution uses For loop as mentioned in the question. String.java has a method indexOf, it can directly be used to obtain the first occurance of the character which is needed to occur before and the character which is needed to occur after. Once both the index are known a simple comparison will give the result.

Function defination:

public boolean isValid( char before, char after , String input);

Next lets see the implementation.

1. Declare two int variables beforeIndex and afterIndex
   


2. In a for loop iterate the input string and for each char check if the character is equal to before, if so update the value of beforeIndex with the currwnt index and break the loop.


3. In an another for loop iterate the input string and for each character check if the current character equals to after. If so then update the value for afterIndex and break. (Assumption if before= '(' and after = ')' then for input = "ab)d(e)" function returns false, if this assumption is wrong then let the loop for step 3 continue to its completion and do not break).


4. return afterIndex > beforeIndex
   

Below is the function implementing above steps

public boolean isValid( char before, char after , String input)
 int beforeIndex = 0, afterIndex = 0;
 for( int i = 0; i < input.length(); i++)
 if(input.charAt(i) == before) 
 beforeIndex = i;
 break;
 
 
 for( int i = 0; i < input.length(); i++)
 if(input.charAt(i) == after) 
 afterIndex = i;
 break;
 
 
 return afterIndex > beforeIndex;
 

You can just loop on the String, when you encounter the ‘)’ set a boolean to true, then on the next iteration, if the boolean is true check if the current char equals to your last char, if so feturn true else set the boolean to false and keep going. Here’s a method that would do the job:

public boolean checkChar(String first, String last, String s) 
 boolean check = false;
 for(int i = 0; i < s.length(); i++) 
 if (check) 
 if(s.charAt(i).equals(last)) return true;
 else check = false;
 else if(s.charAt(i).equals(first) check = true; 
 
 return false;