HDU 3999 (13.07.07)

Problem Description

As we know,the shape of a binary search tree is greatly related to the order of keys we insert. To be precisely:
1.  insert a key k to a empty tree, then the tree become a tree with
only one node;
2.  insert a key k to a nonempty tree, if k is less than the root ,insert
it to the left sub-tree;else insert k to the right sub-tree.
We call the order of keys we insert “the order of a tree”,your task is,given a oder of a tree, find the order of a tree with the least lexicographic order that generate the same tree.Two trees are the same if and only if they have the same shape.

 

Input

There are multiple test cases in an input file. The first line of each testcase is an integer n(n <= 100,000),represent the number of nodes.The second line has n intergers,k1 to kn,represent the order of a tree.To make if more simple, k1 to kn is a sequence of 1 to n.

 

Output

One line with n intergers, which are the order of a tree that generate the same tree with the least lexicographic.

 

Sample Input

41 3 4 2

 

Sample Output

1 3 2 4此题建树的规则在Description中给出按要求建树即可而要求字典序, 用前序遍历即可~ 水!
#include<stdio.h>typedef struct Node{    int num;    struct Node *l;    struct Node *r;}node;node *tree;int isfirst = 1;node* creatTree(node *root, int n) {    if(root == NULL) {        root = new node;        root->num = n;        root->l = NULL;        root->r = NULL;        return root;    }    else {        if(root->num > n)            root->l = creatTree(root->l, n);        else            root->r = creatTree(root->r, n);    }    return root;}void print(node *root) {    if(isfirst) {        printf("%d", root->num);        isfirst = 0;    }    else        printf(" %d", root->num);}void search(node *root) {    if(root != NULL) {        print(root);        search(root->l);        search(root->r);    }}int main() {    int i, n, date;    while(scanf("%d", &n) != EOF) {        isfirst = 1;        for(i = 0; i < n; i++) {            scanf("%d", &date);            tree = creatTree(tree, date);        }        search(tree);        printf("\n");    }    return 0;}