public class Solution {
public boolean isValid(String s) {
Stack<Character> stack = new Stack<Character> ();
for (int i=0; i<s.length(); i++) {
if (s.charAt(i)=='(' || s.charAt(i)=='[' || s.charAt(i)=='{') stack.push(s.charAt(i));
else {
if (stack.empty()) return false;
Character temp = stack.peek();
if (s.charAt(i)==')' && temp!='(') return false;
if (s.charAt(i)==']' && temp!='[') return false;
if (s.charAt(i)=='}' && temp!='{') return false;
stack.pop();
}
}
return stack.empty();
}
}
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