已知二叉树的先序遍历和中序遍历序列求后序遍历序列

               

package algorithm01;

import java.util.Scanner;

/**
 * 给出先序遍历和中序遍历序列求出二叉树的后续遍历序列
 * @author wxisme
 *
 */

public class ToReverse {

	public static void main(String[] args) {
		Scanner scan = new Scanner(System.in);
		String s1, s2;
		while(scan.hasNext()) {
			s1 = scan.next();
			s2 = scan.next();
			build(s1.length(), 0, 0, s1, s2);
			
		}
	}
	
	public static void build(int n, int s1_at, int s2_at, String s1, String s2) {
		if(n <= 0) return;
		//求出根节点在中序遍历中的位置
		int p = s2.indexOf(s1.charAt(s1_at)) - s2_at;
		//后续遍历左子树
		build(p, s1_at+1, s2_at, s1, s2);
		//后续遍历右子树
		build(n-p-1, s1_at+p+1, s2_at+p+1, s1, s2);
		//访问根节点
		System.out.print(s1.charAt(s1_at));
	}

}

 测试：

   DBACEGF ABCDEFG
   ACBFGED
   BCAD CBAD
   CDAB