p20

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LeetCode p20 Valid Parentheses 题解

1.题目：

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.

题意：

判断一个字符串内的所有括号是否搭配得当。

2.解题思路:

使用栈匹配

3.代码

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public class Solution {
    public boolean isValid(String s) {
        Stack<Character> stack = new Stack<Character>();
		String x = "([{";
		String y = ")]}";
		for (char a : s.toCharArray()) {
			// System.out.println(a);
			if (stack.size() != 0) {
				int i = x.indexOf(stack.peek());
				if (i < 0)
					return false;
				if (i == y.indexOf(a)) {
					stack.pop();
				} else {
					stack.add(a);
				}
			} else {
				stack.add(a);
			}
		}
		return stack.size() == 0 ? true : false;
    }
}

4.一些总结：