leetcode20 判断括号是否成对出现

判断括号是否成对出现

判断一个字符串中的括号是否成对出现
该题的核心思路在于使用栈。

该方法虽然不是最优解 可是思路仍是比较清晰的

/**
 * @author rale
 * 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.
 * **/
public class Solution1 {
    public boolean isValid(String s) {
        char[] list = s.toCharArray();
        Stack<Character> stack = new Stack<Character>();
        for(char temp : list){
            if(temp=='(' || temp=='[' || temp=='{'){
                stack.push(temp);
            }
            if(temp=='}' && (stack.isEmpty()||stack.pop()!='{')){
                return false;
            }
            if(temp==')' && (stack.isEmpty()||stack.pop()!='(')){
                return false;
            }
            if(temp==']'&& (stack.isEmpty()||stack.pop()!='[')){
                return false;
            }
        }
        if(!stack.isEmpty()){
            return false;
        }
        return true;
    }
}

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