Checking whether the paranthesis are balanced in the expression

Problem

Checking whether the paranthesis are balanced in the expression

Solution
Method 1 - Using stacks
Stacks can be used to compare the paranthesis. Whenever we find the opening paranthesis we push it in the stack, and whenever we find closing paranthesis, we pop it out from stack. When the expression finishes and stack is not empty, then it means that paranthesis are not balanced otherwise they are.

Example 1
Consider the following expression {([])}

Example 2

Example 3

Example 4

Pseudocode

Algorithm checkBalance(expression)  
// Returns true if the parentheses, brackets,   
    and braces in an expression are paired correctly.  
isBalanced = true  
while ( (isBalanced == true) and not at end of expression)  
{ nextCharacter = next character in expression  
 switch (nextCharacter)  
 { case '(': case '\[': case '{':  
   Push nextCharacter onto stack  
   break  
  case ')': case '\]': case '}':  
   if (stack is empty)  isBalanced = false  
   else  
   { openDelimiter = top of stack  
    Pop stack  
    isBalanced = true or false according to whether openDelimiter and  
     nextCharacter are a pair of delimiters  
   }  
   break  
 }  
}  
if (stack is not empty)  isBalanced = false  
return isBalanced

Thanks

See also