[NOIP 2001 普及组] 求先序排列 Java

import java.util.*;public class Main {public static void main(String[] args) {Scanner sc = new Scanner(System.in);String infixOrder = sc.nextLine(); // 中序String postOrder = sc.nextLine(); // 后序sc.close();System.out.println(preOrder(infixOrder, postOrder));}static String preOrder(String infix, String post) {if (infix.isEmpty() || post.isEmpty()) return ""; // 递归终止char root = post.charAt(post.length() - 1); // 后序最后一个一定是根节点int rootIndex = infix.indexOf(root); // 根节点索引// 中序：左子树→根节点→右子树String infixLeft = infix.substring(0, rootIndex); // 中序的左子树String infixRight = infix.substring(rootIndex + 1); // 中序的右子树，不包含中间的根节点// 后序：左子树→右子树→根节点String postLeft = post.substring(0, infixLeft.length()); // 后序的左子树String postRight = post.substring(infixLeft.length(), post.length() - 1); // 后序的右子树，不包含最后的根节点// 前序：根节点→左子树→右子树return root + preOrder(infixLeft, postLeft) + preOrder(infixRight, postRight); // 左右子树分别递归继续执行}
}

每日一水~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~