Suppose that all the keys in a binary tree are distinct positive integers. Given the postorder and inorder traversal sequences, you are supposed to output the level order traversal sequence of the corresponding binary tree.
Input Specification:
Each input file contains one test case. For each case, the first line gives a positive integer N (≤30), the total number of nodes in the binary tree. The second line gives the postorder sequence and the third line gives the inorder sequence. All the numbers in a line are separated by a space.
Output Specification:
For each test case, print in one line the level order traversal sequence of the corresponding binary tree. All the numbers in a line must be separated by exactly one space, and there must be no extra space at the end of the line.
Sample Input:
7
2 3 1 5 7 6 4
1 2 3 4 5 6 7
Sample Output:
4 1 6 3 5 7 2
解题思路:
思路见模板:https://blog.youkuaiyun.com/alex1997222/article/details/86600086
#include <iostream>
#include <algorithm>
#include <vector>
#include <queue>
using namespace std;
const int MAXN = 60;
struct Node {
int data;
Node* lchild;
Node* rchild;
Node(int _data) {
data = _data;
lchild = rchild = nullptr;
}
};
int preArrays[MAXN], inArrays[MAXN], postArrays[MAXN];
Node* CreateTree(int postL, int postR, int inL, int inR) {
if (postL > postR) return nullptr;
int curPostRoot = postArrays[postR];
Node* root = new Node(curPostRoot);
int curInRoot = -1;
int k;
for (k = inL; k <= inR; ++k) {
if (inArrays[k] == curPostRoot) {
curInRoot = inArrays[k];
break;
}
}
if (curInRoot == -1) return nullptr;
int numleft = k - inL;
root->lchild = CreateTree(postL,postL+numleft-1,inL,k-1);
root->rchild = CreateTree(postL+numleft,postR-1,k+1,inR);
return root;
}
void LayerTravas(Node* root) {
queue<Node*> Bfs_queue;
Bfs_queue.push(root);
bool flag = true;
while (!Bfs_queue.empty()) {
Node* tempNode = Bfs_queue.front();
if (flag) {
cout << tempNode->data;
flag = !flag;
}
else {
cout <<" "<<tempNode->data;
}
Bfs_queue.pop();
if (tempNode->lchild != nullptr) Bfs_queue.push(tempNode->lchild);
if (tempNode->rchild != nullptr) Bfs_queue.push(tempNode->rchild);
}
}
int main() {
int N;
cin >> N;
for (int i = 0; i < N; ++i) {
cin >> postArrays[i];
}
for (int i = 0; i < N; ++i) {
cin >> inArrays[i];
}
Node* troot = CreateTree(0, N - 1,0,N-1);
LayerTravas(troot);
system("PAUSE");
return 0;
}