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用java写一个函数判断字符串中"{"与"}"匹配？
提示："{"与"}"必须同时出现，"{"必须在"}"前面，允许嵌套

解法一：

public class T {public static boolean isMatch(String value) {int numCount = 0, numMatch = 0;for (int i=0; null != value && i<value.length(); i++) {char ch = value.charAt(i);if (ch == '{') {numCount ++;numMatch ++;} else if (ch == '}') {numCount --;}if (numCount < 0) {return false;}}return (numMatch > 0 && numCount == 0);}public static void main(String args[]) {System.out.println( "=========must false=====" );System.out.println( isMatch(null) );System.out.println( isMatch("") );System.out.println( isMatch("ddddd") );System.out.println( isMatch("d{dddd") );System.out.println( isMatch("dd{}}ddd") );System.out.println( isMatch("d}dd{dd") );System.out.println( "=========must true=====" );System.out.println( isMatch("dd{}ddd") );System.out.println( isMatch("ddd{{}d}d") );System.out.println( isMatch("d{d{d}d}d") );}}

 

解法二：考虑用栈

import java.util.LinkedList;public class CurlyBracesMatcher{private LinkedList<Character> stack = new LinkedList<Character>();/** * @param args */public static void main(String[] args){CurlyBracesMatcher matcher = new CurlyBracesMatcher();System.out.println(matcher.matches("{{{{}}a}a}"));}public boolean matches(String string){if (string == null || string.length() == 0 || string.trim().equals(""))return true;int i = 0;while (i < string.length()){char ch = string.charAt(i);if (ch == '{'){stack.push(ch);}else if (ch == '}'){if (stack.isEmpty())return false;stack.pop();}i++;}if (!stack.isEmpty())return false;return true;}}