Given a string s 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.
class Solution {
public boolean isValid(String s) {
Stack<Character> stack = new Stack<>();
Map<Character, Character> map = new HashMap<Character, Character>() {
{
put('}', '{');
put(']', '[');
put(')', '(');
}
};
for (Character c : s.toCharArray()) { // 顺序读取字符
if (!stack.isEmpty() && map.containsKey(c)) { // 是右括号 && 栈不为空
if (stack.peek() == map.get(c)) { // 取其对应的左括号直接和栈顶比
stack.pop(); // 相同则抵消，出栈
} else {
return false; // 不同则直接返回
}
} else {
stack.push(c); // 左括号，直接入栈
}
}
return stack.isEmpty(); // 看左右是否抵消完
}
}
class Solution {
public boolean isValid(String s) {
while (s.contains("[]") || s.contains("{}") || s.contains("()")){
s = s.replace("[]","");
s = s.replace("()","");
s = s.replace("{}","");
}
return s == "";
}
}
