UVa 548 Tree

import java.io.*;
import java.util.*;

class Node {
	int val;
	Node left;
	Node right;
	public Node(int val) {
		this.val = val;
	}
}



public class Main {
	static Integer[] inorder;
	static Integer[] postorder;

	
	public static List<Integer> findminpath(Node root) {
		if(root.left == null && root.right == null) {
			List<Integer> res= new ArrayList<Integer>();
			res.add(root.val);
			return res;
		}
		else if(root.left != null && root.right != null) {
			List<Integer> l = findminpath(root.left);
			List<Integer> r = findminpath(root.right);
			int sum1 = 0, sum2 = 0;
			for(Integer i: l) sum1 += i;
			for(Integer i: r) sum2 += i;
			if(sum1 < sum2) {l.add(root.val); return l;}
			else {r.add(root.val); return r;}
		}
		else if(root.left == null && root.right != null) {
			List<Integer> r = findminpath(root.right);
			r.add(root.val); 
			return r;
		}
		else {
			List<Integer> l = findminpath(root.left);
			l.add(root.val); 
			return l;
		}
	}
	
	public static Node createTree(int istart, int pstart, int length) {
		if(length < 1) return null;
		int value = postorder[pstart + length - 1];
		Node root = new Node(value);
		int i;
		for(i = istart; i < istart + length; i++)
			if(inorder[i] == value) break;
		root.left = createTree(istart, pstart, i - istart);
		root.right = createTree(i + 1, pstart + i - istart, length - i + istart - 1);
		return root;
	}
	
	public static void transerval(Node rt) {
		if(rt == null) return;
		System.out.print(rt.val+ " ");
		transerval(rt.left);
		transerval(rt.right);
	}
	
	public static void main(String[] args) {
		Scanner cin = new Scanner(System.in);
		while(cin.hasNextLine()) {
			String tmp = cin.nextLine();
			String[] in = tmp.split(" ");
			tmp = cin.nextLine();
			String[] post = tmp.split(" ");
			int n = in.length;
			inorder = new Integer[n];
			postorder = new Integer[n];
			for(int i = 0; i < n; i++) {
				inorder[i] = Integer.parseInt(in[i]);
				postorder[i] = Integer.parseInt(post[i]);
			}
			Node root = createTree(0, 0, n);
			List<Integer> result = findminpath(root);
			System.out.println(result.get(0));
		}
	}
}