LeetCode每日一题:valid parentheses
2017-07-05 本文已影响20人
yoshino
问题描述
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.
问题分析
括号匹配问题一般都用栈实现。
代码实现
public boolean isValid(String s) {
if (s.length() == 0) return true;
Stack<Character> stack = new Stack<>();
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.isEmpty() || (s.charAt(i) == ')' && stack.pop() != '(')
|| (s.charAt(i) == '}' && stack.pop() != '{')
|| (s.charAt(i) == ']' && stack.pop() != '[')) {
return false;
}
}
}
if (stack.isEmpty()) return true;
else return false;
}