PAT-A 1020. Tree Traversals

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:

72 3 1 5 7 6 41 2 3 4 5 6 7

Sample Output:

4 1 6 3 5 7 2

程序代码：

#include<stdio.h>#include<stdlib.h>#define MAX 1000struct ListNode{    int data;    struct ListNode* left;    struct ListNode* right;};typedef struct ListNode node;struct queue{    node n[1000];    node* s;    node* e;};node* create(int post[],int postStart,int postEnd,int in[],int inStart,int inEnd);node* pop(struct queue* a);void push(struct queue* a,node* b);void layerprint(node* r,int n);int post[MAX],in[MAX], ans[MAX];int main(){    int i,n;    scanf("%d",&n);    for(i=0;i<n;i++)    {        scanf("%d",&post[i]);    }        for(i=0;i<n;i++)        {                scanf("%d",&in[i]);        }    node* r = create(post,0,n-1,in,0,n-1);    layerprint(r,n);    return 0;}node* create(int post[],int postStart,int postEnd,int in[],int inStart,int inEnd){    if(postStart>postEnd)        return NULL;    else if(inStart>inEnd)        return NULL;    node* r = (node*)malloc(sizeof(node));    r->data = post[postEnd];    int i;    for(i=inEnd;i>=inStart;i--)    {        if(in[i]==post[postEnd])            break;    }    int len = inEnd - i;    r->right = create(post,postEnd-len,postEnd-1,in,i+1,inEnd);    r->left  = create(post,postStart,postEnd-len-1,in,inStart,i-1);    return r;}void layerprint(node* r,int n){    struct queue q1;        //创建队列    q1.s=&q1.n[0];       //初始化队列    q1.e=&q1.n[0];    node* p;     //临时结点指针    int count =0;    push(&q1,r);              //根节点入队    while(q1.e!=q1.s)       //判断队列是否为空    {        p = pop(&q1);           //出队        printf("%d",p->data);      //访问结点        count++;        if(count!=n)                putchar(' ');        if(p->left !=NULL)            push(&q1,p->left);        //左儿子入队        if(p->right!=NULL)            push(&q1,p->right);       //右儿子入队    }}node* pop(struct queue* a){    node *tmp=(node*)malloc(sizeof(node));    *tmp = *a->s;    a->s++;    return tmp;}void push(struct queue* a,node* b){    *a->e=*b;    a->e++;}