1127. ZigZagging on a Tree (30) 根据中+后输出层序遍历

Suppose that all the keys in a binary tree are distinct positive integers. A unique binary tree can be determined by a given pair of postorder and inorder traversal sequences. And it is a simple standard routine to print the numbers in level-order. However, if you think the problem is too simple, then you are too naive. This time you are supposed to print the numbers in "zigzagging order" -- that is, starting from the root, print the numbers level-by-level, alternating between left to right and right to left. For example, for the following tree you must output: 1 11 5 8 17 12 20 15.

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 inorder sequence and the third line gives the postorder sequence. All the numbers in a line are separated by a space.

Output Specification:

For each test case, print the zigzagging sequence of the tree in a line. 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:

812 11 20 17 1 15 8 512 20 17 11 15 8 5 1

Sample Output:

1 11 5 8 17 12 20 15

模板建立好树

然后奇数层倒着输出，偶数层正向输出

#include<iostream>#include<cstdio>#include<algorithm>#include<vector>#include<set>#include<queue>#include<cstring>#include<map>using namespace std;typedef struct tree{int num;struct tree *left,*right;}tree,*linktree; linktree creat(int *hou,int *zhong,int n){if(n<=0) return NULL;linktree t=new tree();t->num=hou[n-1];int index=0;for(int i=0;i<n;i++){if(zhong[i]==hou[n-1]){index=i;break;}}t->left=creat(hou,zhong,index);t->right=creat(hou+index,zhong+index+1,n-index-1);return t;}vector<int> v[1000];typedef pair<int,linktree> P;void cengxu(linktree head){queue<P> que;que.push({1,head});while(que.size()){P p=que.front();que.pop();int num=p.first;linktree fz=p.second;if(fz->left!=NULL) {que.push({num+1,fz->left});v[num+1].push_back(fz->left->num);}if(fz->right!=NULL) {que.push({num+1,fz->right});v[num+1].push_back(fz->right->num);}}}int main(){int n;scanf("%d",&n);int zhong[100],hou[100];for(int i=0;i<n;i++){scanf("%d",&zhong[i]);}for(int i=0;i<n;i++){scanf("%d",&hou[i]);}linktree head=creat(hou,zhong,n);cengxu(head);printf("%d",head->num);for(int i=2;i<=30;i++){if(i%2==0){for(int j=0;j<v[i].size();j++) printf(" %d",v[i][j]);}else for(int j=v[i].size()-1;j>=0;j--) printf(" %d",v[i][j]);}return 0;}