1099. Build A Binary Search Tree (30)

1099. Build A Binary Search Tree (30)
时间限制 100 ms 内存限制 65536 kB 代码长度限制 16000 B
判题程序 Standard 作者 CHEN, Yue

A Binary Search Tree (BST) is recursively defined as a binary tree which has the following properties:
The left subtree of a node contains only nodes with keys less than the node’s key.
The right subtree of a node contains only nodes with keys greater than or equal to the node’s key.
Both the left and right subtrees must also be binary search trees.
Given the structure of a binary tree and a sequence of distinct integer keys, there is only one way to fill these keys into the tree so that the resulting tree satisfies the definition of a BST. You are supposed to output the level order traversal sequence of that tree. The sample is illustrated by Figure 1 and 2.

Input Specification:
Each input file contains one test case. For each case, the first line gives a positive integer N (<=100) which is the total number of nodes in the tree. The next N lines each contains the left and the right children of a node in the format “left_index right_index”, provided that the nodes are numbered from 0 to N-1, and 0 is always the root. If one child is missing, then -1 will represent the NULL child pointer. Finally N distinct integer keys are given in the last line.
Output Specification:
For each test case, print in one line the level order traversal sequence of that tree. All the numbers must be separated by a space, with no extra space at the end of the line.
Sample Input:
9
1 6
2 3
-1 -1
-1 4
5 -1
-1 -1
7 -1
-1 8
-1 -1
73 45 11 58 82 25 67 38 42
Sample Output:
58 25 82 11 38 67 45 73 42

#define _CRT_SECURE_NO_WARNINGS
#include <algorithm>
#include <iostream>
#include <cstdio>
#include <iomanip>
#include <queue>


using namespace std;

const int MaxN = 110;
int seq[MaxN],cur = 0;

typedef struct tnode
{
    int data;
    struct tnode * lchild;
    struct tnode * rchild;
}TNode;

TNode * Ptr[MaxN] = { 0 };

void Inorder(TNode * root)
{
    if (!root) return;

    Inorder(root->lchild);
    root->data = seq[cur++];
    Inorder(root->rchild);
}


TNode * CreateTree(int n)
{
    for (int i = 0; i < n; ++i)
    {
        Ptr[i] = new TNode;
        Ptr[i]->lchild = Ptr[i]->rchild = NULL;
    }

    for (int i = 0; i < n; ++i)
    {
        int left_index, right_index;
        cin >> left_index >> right_index;

        if (left_index != -1)
            Ptr[i]->lchild = Ptr[left_index];

        if (right_index != -1)
            Ptr[i]->rchild = Ptr[right_index];
    }

    for (int i = 0; i < n; ++i)
        cin >> seq[i];
    sort(seq, seq + n);

    Inorder(Ptr[0]);

    return Ptr[0];
}


void LevelOrder(TNode * root)
{
    if (!root) return;
    queue<TNode *>que;
    que.push(root);

    while (que.size())
    {
        TNode * node = que.front(); que.pop();
        if (node->lchild)que.push(node->lchild);
        if (node->rchild)que.push(node->rchild);

        cout << node->data;
        if (que.size())
            cout << " ";
        delete node;
    }
}

int main()
{
#ifdef _DEBUG
    freopen("data.txt", "r+", stdin);
#endif // _DEBUG

    std::ios::sync_with_stdio(false);

    int n;
    cin >> n;

    TNode * root = CreateTree(n);
    LevelOrder(root);

    return 0;
}