L2-011 玩转二叉树

题目链接
相似题目
L2-006 树的遍历

步骤：
1、根据前序遍历和中序遍历建立二叉树
2、递归翻转左右子树
3、使用队列的先进先出性质实现层次遍历（广度优先）

#include<iostream>
#include<stdlib.h>
#include<vector>
#include<queue>
using namespace std;
int A[35];
int B[35];
int N;
typedef struct TNode {
    
	struct TNode* left;
	struct TNode* right;
	int data;
}*Tree;
Tree BuildTree(int X[],int Y[],int n) {
    		//建立二叉树
	if (n <= 0  )	return NULL;
	int i = 0;
	while (X[i] != Y[0])i++;
	//cout << n << endl;
	Tree p = (Tree)malloc(sizeof(struct TNode));
	p->data = X[i];
	//cout << "left" << endl;
	p->left = BuildTree(X, &Y[1], i);
	//cout << "right" << endl;
	p->right = BuildTree(&X [ i + 1], &Y [ i + 1], n - i - 1);
	
	return p;
}
void Reverse(Tree& T) {
    			//翻转左右子树
	if (T == NULL)	return;
	Reverse(T->left);
	Reverse(T->right);
	TNode* temp = T->left;
	T->left = T->right;
	T->right = temp;
}
vector<int> Level(Tree T) {
    			//层次遍历
	queue<TNode*> Q;
	vector<int> ans;
	Q.push(T);
	while (!Q.empty()) {
    
		TNode* p = Q.front();
		Q.pop();
		if (p->left != NULL)	Q.push(p->left);
		if (p->right != NULL)Q.push(p->right);
		ans.push_back(p->data);
	}
	return ans;
}
int main() {
    
	cin >> N;
	for (int i = 0; i < N; i++) cin >> A[i];
	for (int i = 0; i < N; i++) cin >> B[i];
	Tree root = BuildTree(A, B, N);
	Reverse(root);
	vector<int> ans = Level(root);
	for (int i = 0; i < N; i++) {
    
		cout << ans[i];
		if (i != N - 1)	cout << " ";
	}
	return 0;
}