leetcode Valid Parentheses 2.8 难度系数2

yundomo

于 2014-01-26 12:23:45 发布

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本文介绍了一种使用Java实现的有效括号匹配验证算法。通过利用栈数据结构，该算法能够检查包含括号的字符串是否有效，即括号是否按正确的顺序闭合。例如，'()[]{}

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Question:

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.

import java.util.Stack;
public class Solution {
    public boolean isValid(String s) {
        Stack<Character> st = new Stack<Character>();
    	for(int i = 0;i<s.length();i++){
    		char c = s.charAt(i);
    		if (c=='{'||c=='['||c=='(') {
				st.push(c);
			}else if (c=='}'||c==')'||c==']') {
				if (st.size()==0) {
					return false;
				}
				char popChar = st.pop();
				if (popChar=='{'&&c=='}') {
					continue;
				}else if (popChar=='('&&c==')') {
					continue;
				}else if (popChar=='['&&c==']'){
					continue;
				}
				return false;
			}
    	}
    	
    	return st.size()==0;
    }
}