一道考研题

第58题。数据输入换成数字，方便点，先建立二叉树再输出。

 

#include<iostream>
#include<queue>
using namespace std;
struct node {
	int data;
	node* lchild;
	node* rchild;
};
const int maxn = 35;
int pos[maxn];
int in[maxn];
int n;
node* create(int posl, int posr, int inl, int inr) {
	if (posl > posr) return NULL;
	node* root = new node;
	root->data = pos[posr];
	int k;
	for (k = inl; k <= inr; k++) {
		if (in[k] == pos[posr]) {
			break;
		}
	}
	int numleft = k - inl;
	root->lchild = create(posl, posl + numleft - 1, inl, k - 1);
	root->rchild = create(posl + numleft, posr - 1, k + 1, inr);
	return root;
}

void bfs2(node* root) {
	queue<node*> q;
	q.push(root);
	while (!q.empty()) {
		node* now = q.front();
		q.pop();
		printf("%d ", now->data);
		if (now->rchild != NULL) q.push(now->rchild);
		while (now->lchild != NULL) {
			if (now->lchild->rchild != NULL) q.push(now->lchild->rchild);
			if (now->lchild->data < q.front()->data) {
				printf("%d ", now->lchild->data);
			}
			else {
				q.push(now->lchild);
				break;
			}
			now = now->lchild;
		}
	}
}

int main() {
	scanf("%d", &n);
	for (int i = 1; i <= n; i++) {
		int t;
		scanf("%d", &t);
		pos[i] = t;
	}
	for (int i = 1; i <= n; i++) {
		int t;
		scanf("%d", &t);
		in[i] = t;
	}
	node* root = create(1, n, 1, n);
	bfs2(root);

	return 0;
}