Given a string containing just the characters '(', ')', '{', '}', '[' and ']', determine if the input string is valid.
An input string is valid if:
Open brackets must be closed by the same type of brackets. Open brackets must be closed in the correct order. Note that an empty string is also considered valid.
Example 1:
Input: "()"
Output: true
Example 2:
Input: "()[]{}"
Output: true
Example 3:
Input: "(]"
Output: false
Example 4:
Input: "([)]"
Output: false
Example 5:
Input: "{[]}"
Output: true
class Solution {
public boolean isValid(String s) {
Map<Character,Character> map=new HashMap<>();
map.put(')','(');
map.put(']','[');
map.put('}','{');
Stack<Character> stack=new Stack<>();
for(char ch:s.toCharArray()){
if(map.containsKey(ch)){
if(!stack.isEmpty() && stack.peek()==map.get(ch)){
stack.pop();
}
else
return false;
}
else
stack.push(ch);
}
return stack.size()==0?true:false;
}
}