Uva536——Tree Recovery

根据先序遍历以及中序遍历，构造二叉树，输出后序遍历。

代码：

#include <iostream>
#include <cstring>
#include <stdlib.h>
using namespace std;


struct node
{
	char c;
	struct node *lchild, *rchild;
};

node *Root;
int len;
char pre[30], in[30];
void create(node *&root, int p1, int p2, int i1, int i2)  //递归构造二叉树
{
	if(i1 > i2)
		return;

	char c = pre[p1];
	int i = i1;
	while(in[i] != c) i++;

	int cnt = i - i1;
	root = new node();
	root->c = c;
	root->lchild = root->rchild = NULL;
	create(root->lchild, p1 + 1, p1 + cnt, i1, i1 + cnt - 1);
	create(root->rchild, p1 + cnt + 1, p2, i1 + cnt + 1, i2);
}

void post_order(node *s)  //后序遍历
{
	if(s == NULL)
		return;
	post_order(s->lchild);
	post_order(s->rchild);
	cout << s->c;
}

void destory(node *s)     //释放构造的二叉树
{
	if(s == NULL)
		return;
	destory(s->lchild);
	destory(s->rchild);
	free(s);
}

int main()
{
//	freopen("1.txt", "r", stdin);
	while(cin >> pre >> in)
	{
		destory(Root);
		len = strlen(pre);
		create(Root, 0, len - 1, 0, len - 1);
		post_order(Root);
		cout << endl;
	}
	return 0;
}