#20. Valid Parentheses [LeetCode Grind 75 in Java]
[Problem Link] https://leetcode.com/problems/valid-parentheses/
class Solution {
public boolean isValid(String s) {
Stack<Character> st = new Stack<>();
for(char c : s.toCharArray()){
if(c == '(' || c == '{' || c == '[') st.push(c);
else{
if(st.isEmpty()) return false;
char top = st.peek();
if(c == ')' && top != '(') return false;
if(c == '}' && top != '{') return false;
if(c == ']' && top != '[') return false;
st.pop();
}
}
if(!st.isEmpty()) return false;
return true;
}
}