推断二叉树(递推)

推断二叉树

已知前序中序求后序

#include<cstring>
#include<cstdio>
#include<iostream>
using namespace std;
void binary_tree(string mid, string pre) {
	if (mid.size() > 0) {
		char ch = pre[0];
		int cur = mid.find(ch);
		binary_tree(mid.substr(0, cur), pre.substr(1, cur));
		binary_tree(mid.substr(cur + 1), pre.substr(cur + 1));
		cout << ch;
	}
}

int main() {
	string a, b;
	cin >> a >> b;
	binary_tree(a, b);
	return 0;
}

已知后序中序求前序

#include<cstring>
#include<cstdio>
#include<iostream>
using namespace std; void binary_tree(string mid, string last)
{
	if (mid.size() > 0)
	{
		char ch = last[last.size() - 1];
		cout << ch;
		int cur = mid.find(ch);
		binary_tree(mid.substr(0, cur), last.substr(0, cur));
		binary_tree(mid.substr(cur + 1), last.substr(cur, last.size() - cur - 1));
	}
}

int main()
{
	string a, b;
	cin >> a >> b;
	binary_tree(a, b);
	return 0;
}

处理两位数的情况

#include<iostream>
using namespace std;
#include<string>
string last = "";
string mid = "";

void binary_tree(string mid, string last)
{
	if (mid.size() > 0)
	{
		cout << " ";
		char ch = last[last.size() - 1];
		int chout = last[last.size() - 1] - '0';
		cout << chout;
		int cur = mid.find(ch);
		binary_tree(mid.substr(0, cur), last.substr(0, cur));
		binary_tree(mid.substr(cur + 1), last.substr(cur, last.size() - cur - 1));
	}
	else return;
}


int main() {
	int n;
	cin >> n;
	for (int i = 1; i <= n; i++)
	{
		int x;
		cin >> x;
		last += x + '0';//处理两位数的情况
	}
	for (int i = 1; i <= n; i++)
	{
		int x;
		cin >> x;
		mid += x + '0';
	}
	cout << "Preorder:";
	binary_tree(mid, last);
	return 0;
}

7
2 3 1 5 7 6 4
1 2 3 4 5 6 7

Preorder: 4 1 3 2 6 5 7

绕行踩点法：
先序遍历经过结点左侧时踩点
中序遍历经过结点底部时踩点
后序遍历经过结点右侧时踩点