Bracket Match Problem(括号匹配问题)

Posted 2021-09-07 Dream_it_possible！

Question

        Given a string, which is combined with '(',')''[',']','{','}', please follow the rules below to determine weather the string is matched.

example

one:

Input:  "()"

Output: true

two:

Input: "(())[][]"

Output: true

three:

Input:  "()([]"

Output: false

Thinking 

        If you observe carefully, then you will find every pair of parentheses are symmetrical, it is a good choice to use statck to help us solve this problem, why? 

        Stack has a first-in first-out feature, so we can push left bracket in the stack, and we could get a compare when get the right bracket, if matched until the end of the loop, return true, otherwise return false.

        once the loop is over, we can judge whether it meets the requirement according to the size of stack, if  the size of stack is zero, return true, otherwise, return false.

package leetcode100;

import java.util.Stack;

/**
 * @author bingbing
 * @date 2021/8/19 0019 14:09
 * 括号匹配问题。
 * Given a string, which is combined with '(',')''[',']','{','}',
 * please follow the rules below to determine whether the string is matched
 * example:
 * Input: "()"
 * Output: true
 * <p>
 * Input:"(())[][]"
 * Output: true
 * <p>
 * Input:"()([]"
 * Output:false
 */
public class BracketMatchProblem {


    public static void main(String[] args) {

        String str = "(){}[][][]()";
        boolean match = matchBracketProblem(str);
        System.out.println("The brackets matched id :" + match);

    }

    private static boolean matchBracketProblem(String str) {

        Stack<Character> stack = new Stack<>();
        for (int i = 0; i < str.length(); i++) {
            char c = str.charAt(i);
            if (c == '(' || c == '[' || c == '{') {
                stack.push(c);
            } else {
                if (!stack.isEmpty()) {
                    Character element = stack.pop();
                    char left = '(';
                    switch (c) {
                        case ')':
                            left = '(';
                            break;
                        case ']':
                            left = '[';
                            break;
                        case '}':
                            left = '{';
                            break;
                        default:
                            break;
                    }
                    if (left != element) {
                        return false;
                    }
                } else {
                    return true;
                }
            }
        }

        if (stack.size() == 0) {
            return true;
        }
        return false;
    }
}

 Test

Input:   "(){}[][][]()"

Output: true

 

Input:  "(){}[]([][]()"

Output: false