PROBLEM DESCRIPTION
Given an expression string x. Examine whether the pairs and the orders of {,},(,),[,] are correct in exp. For example, the function should return ‘true’ for exp = [()]{}{[()()]()} and ‘false’ for exp = [(]).
Note: The drive code prints “balanced” if function return true, otherwise it prints “not balanced”.
SOLUTION
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class Solution
{
//Function to check if brackets are balanced or not.
static boolean ispar(String x)
{
Map<Character, Character> brackets = new HashMap<>();
brackets.put(')', '(');
brackets.put('}', '{');
brackets.put(']', '[');
Stack<Character> stack = new Stack<>();
for(int i=0; i<x.length(); i++){
char ch = x.charAt(i);
// we got a closing bracket
if(brackets.containsKey(ch)){
// check if it has corresponding open bracket in stack
if(!stack.isEmpty() && brackets.get(ch) == stack.peek()){
stack.pop();
}else
return false;
}else{
stack.push(ch);
}
}
return stack.isEmpty();
}
}