转载自：http://blog.csdn.net/u012706811/article/details/50791858
java.util包中提供了stack这个类,可以利用堆栈解决很多问题,比如经典的括号匹配问题
先看看stack这个类
方法
例题:
描述现在，有一行括号序列，请你检查这行括号是否配对。输入第一行输入一个数N（N 0-100）,表示有N组测试数据。后面的N行输入多组输入数据，每组输入数据都是一个字符串S(S的长度小于10000，且S不是空串），测试数据组数少于5组。数据保证S中只含有"[","]","(",")"四种字符输出每组输入数据的输出占一行，如果该字符串中所含的括号是配对的，则输出Yes,如果不配对则输出No样例输入3[(])(])([[]()])样例输出NoNoYes
思路:
当匹配到左括号则压栈
匹配到右括号,则和栈顶元素比较,匹配一对则出栈,否则返回No,结束判断
栈空还没匹配完,也返回No,结束判断
<code class="hljs java has-numbering" style="display: block; padding: 0px; background-color: transparent; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-top-left-radius: 0px; border-top-right-radius: 0px; border-bottom-right-radius: 0px; border-bottom-left-radius: 0px; word-wrap: normal; background-position: initial initial; background-repeat: initial initial;"><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">package</span> com.day1;<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">import</span> java.util.Scanner;<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">import</span> java.util.Stack;<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> <span class="hljs-class" style="box-sizing: border-box;"><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">class</span> <span class="hljs-title" style="box-sizing: border-box; color: rgb(102, 0, 102);">Main</span> {</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">static</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">void</span> <span class="hljs-title" style="box-sizing: border-box;">main</span>(String[] args) { Scanner input = <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> Scanner(System.in); <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">int</span> n = input.nextInt(); String[] arr = <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> String[n]; <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">for</span> (<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">int</span> i = <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0</span>; i < arr.length; i++) { arr[i] = input.next(); } <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">for</span> (String string : arr) { System.out.println(isMatch(string)); } } <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">private</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">static</span> String <span class="hljs-title" style="box-sizing: border-box;">isMatch</span>(String str){ Stack<Character> stack = <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> Stack<>();<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//建立栈</span> <span class="hljs-javadoc" style="color: rgb(136, 0, 0); box-sizing: border-box;">/** * 对字符串逐个扫描 * 遇到左括号入栈,遇到右括号则判断 */</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">for</span> (<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">int</span> i = <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0</span>; i < str.length(); i++) { <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span> (str.charAt(i)!=<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">')'</span> && str.charAt(i)!=<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">']'</span>) { stack.push(str.charAt(i)); }<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">else</span> { <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">///栈空或者不匹配,则返回No</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span> (stack.empty() || !isBracketMatch(stack.peek(), str.charAt(i))) { <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">return</span> <span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"No"</span>; }<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">else</span> { stack.pop(); } } } <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">return</span> <span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"Yes"</span>; } <span class="hljs-javadoc" style="color: rgb(136, 0, 0); box-sizing: border-box;">/** * 判断两个括号是否匹配 *<span class="hljs-javadoctag" style="color: rgb(102, 0, 102); box-sizing: border-box;"> @param</span> c1 *<span class="hljs-javadoctag" style="color: rgb(102, 0, 102); box-sizing: border-box;"> @param</span> c2 *<span class="hljs-javadoctag" style="color: rgb(102, 0, 102); box-sizing: border-box;"> @return</span> */</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">private</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">static</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">boolean</span> <span class="hljs-title" style="box-sizing: border-box;">isBracketMatch</span>(Character c1,Character c2){ <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span> (c1 == <span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">'('</span> && c2 == <span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">')'</span>) { <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">return</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">true</span>; } <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span> (c1 ==<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">'['</span> && c2 ==<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">']'</span>) { <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">return</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">true</span>; } <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">return</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">false</span>; }}</code> 0 0
