poj 2255 二叉树 已知先序和中序，求后序

题目大意：已知二叉树的先序和中序排列，要你求它的后序

解题思路：水题，根据二叉树的性质，递归求解，

DBACEGF ABCDEFG

D为二叉树的根节点， BAC, ABC为以D为根结点的左子树的先序和中序排列，EGF，EFG为以D为根结点的右子树的先序和中序排列。然后递归求解

#include <iostream>
#include <cstdio>
#include <cstring>
using namespace std;

const int maxn = 30;

void postOrder(char *pre, int plen, char *in, int ilen);

int main()
{
	
	char preOrder[maxn], inOrder[maxn];
	int prelen, inlen;
	while(scanf("%s", preOrder) != EOF)
	{
		scanf("%s", inOrder);
		prelen = strlen(preOrder);
		inlen = strlen(inOrder);
		postOrder(preOrder, prelen, inOrder, inlen);
		printf("\n");
	}
	
	return 0;
}

void postOrder(char *preorder, int plen, char *inorder, int ilen)
{
	char *pre = preorder;
	char *in = inorder;
	if(plen == 0)
		return;
	for(int i = 0; i < ilen; i++, in++)
	{
		if(*pre == *in)
			break;
	}
	int l, r;
	l = in - inorder;
	r = ilen - l - 1;
	postOrder(preorder + 1, l, inorder, l);//左子树
	postOrder(preorder + 1 + l, r, in + 1, r);//右子树
	printf("%c", *preorder);
}