Given a string containing just the characters ‘(‘, ‘)’, ‘{‘, ‘}’, ‘[’ and ‘]’, determine if the input string is valid.
The brackets must close in the correct order, “()” and “()[]{}” are all valid but “(]” and “([)]” are not.
给定一个只包括 ‘(‘,’)’,’{‘,’}’,’[‘,’]’ 的字符串,判断字符串是否有效。有效字符串需满足:左括号必须用相同类型的右括号闭合。左括号必须以正确的顺序闭合。
public class Solution {
public boolean isValid(String s) {
Stack<Character> stack = new Stack<>();
for (int i = 0; i < s.length(); i++) {
char c = s.charAt(i);
if (c == '(' || c == '[' || c == '{')
stack.push(c);
else {
if (stack.isEmpty())
return false;
char topChar = stack.pop();
if (c == ')' && topChar != '(')
return false;
if (c == ']' && topChar != '[')
return false;
if (c == '}' && topChar != '{')
return false;
}
}
return stack.isEmpty();
}
}
测试代码
public class Test {
public static void main(String[] args) {
System.out.println((new Solution()).isValid("()[]{}"));
System.out.println((new Solution()).isValid("([)]"));
}
}
运行结果
true
false