已知前序和中序求后续遍历

#include<iostream>
#include<stdio.h>
class Node
{
  public:
	Node * l;
	Node *r;
	int val;
	  Node (int v = 0)
	{
		l = NULL;
		r = NULL;
		val = v;
	}
};
int find_p (int *mid, int val, int i, int j);
void set_tree (Node * &root, int pos, int *pre, int *mid, int left, int right, bool & good);
void print_tree (Node * root);
int main ()
{
	int size;
	while (scanf ("%d", &size) != EOF)
	{
		int *pre = new int[size];
		int *mid = new int[size];
		for (int i = 0; i < size; i++)
			scanf ("%d", &pre[i]);
		for (int j = 0; j < size; j++)
			scanf ("%d", &mid[j]);
		Node *root;
		bool good = true;
		set_tree (root, 0, pre, mid, 0, size - 1, good);
		if(good)
			print_tree (root);
		else
			printf("No");
		printf ("n");
		delete []pre;
		delete []mid;
	}
	return 0;
}
int find_p (int *mid, int val, int i, int j)
{
	for (i; i <= j; i++)
		if (mid[i] == val)
			return i;
	return -1;
}
void set_tree (Node * &root, int pos, int *pre, int *mid, int left, int right, bool & good)
{
	if (left > right)
		return;
	root = new Node (pre[pos]);
	int cur = find_p (mid, pre[pos], left, right);
	if (cur == -1)
		good = false;
	if (!good)
		return;
	set_tree (root->l, pos + 1, pre, mid, left, cur - 1, good);
	set_tree (root->r, pos + cur - left + 1, pre, mid, cur + 1, right, good);
}
void print_tree (Node * root)
{
	if (root == NULL)
		return;
	print_tree (root->l);
	print_tree (root->r);
	printf ("%d ", root->val);
}