栈问题-根据入栈序列，得出可能的出栈序列

根据入栈序列，得出可能的出栈序列

例如：

输入： A B

输出：

A进A出B进B出  AB

A进B进B出A出  BA

 

输入：A B C

输出：

A进A出B进B出C进C出  ABC

A进A出B进C进C出B出  ACB

A进B进C进C出B出A出  CBA

A进B进B出C进C出A出  BCA

A进B进B出A出C进C出  BAC

 

具体函数

public static void printAllPop(List<Object> list) {LinkedList<Object> queue = new LinkedList<Object>(list);LinkedList<Object> stack = new LinkedList<Object>();List<Object> popList = new ArrayList<Object>();StringBuilder sb = new StringBuilder();printAllPop(queue, stack, popList, sb);}private static void printAllPop(LinkedList<Object> queue, LinkedList<Object> stack, List<Object> popList, StringBuilder sb) {// 如果数据源队列为空，则如果数据栈为空说明此系列入栈出栈过程已结束则输出整个过程，反之数据栈不为空则说明数据栈只能进行出栈操作// 如果数据源队列不为空，则如果数据栈为空则说明数据栈只能做入栈操作，反之数据栈又能做入栈操作也有可能做出栈操作，即过程产生分支// 为了两个操作互不影响，在这里用复制相关参数的方法保存现场，让一个操作用参数副本，一个操作用原来的参数if (queue.isEmpty()) {if (stack.isEmpty()) {System.out.println(sb + "  " + popList);} else {popList.add(stack.peekLast());sb.append(stack.pollLast() + "出");printAllPop(queue, stack, popList, sb);}} else {if (stack.isEmpty()) {stack.add(queue.peekFirst());sb.append(queue.pollFirst() + "进");printAllPop(queue, stack, popList, sb);} else {LinkedList<Object> queueCopy = new LinkedList<Object>(queue);LinkedList<Object> stackCopy = new LinkedList<Object>(stack);List<Object> popListCopy = new ArrayList<Object>(popList);StringBuilder sbCopy = new StringBuilder(sb.toString());stackCopy.add(queueCopy.peekFirst());sbCopy.append(queueCopy.pollFirst() + "进");printAllPop(queueCopy, stackCopy, popListCopy, sbCopy);popList.add(stack.peekLast());sb.append(stack.pollLast() + "出");printAllPop(queue, stack, popList, sb);}}}