1099. Build A Binary Search Tree
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
程序代码：
#include<stdio.h>
#include<stdlib.h>
#define MAX 100
typedef struct
{
int data;
int left;
int right;
}node;
typedef struct
{
node value[MAX];
int top;
int bom;
}queue;
void initQueue(queue* s);
void push(queue* s,node tmp);
node pop(queue* s);
void layerPrint(node a[],int len);
int isEmptyQueue(queue*s);
int num[MAX];
int k=0;
int comp(const void* a,const void* b);
void inOrderVisit(node*p,int* num);
node a[MAX];
int main()
{
int num[MAX];
int n,i;
int cnt;
scanf("%d",&n);
for(i=0;i<n;i++)
{
scanf("%d%d",&a[i].left,&a[i].right);
}
for(i=0;i<n;i++)
{
scanf("%d",&num[i]);
}
qsort(num,n,sizeof(int),comp);
inOrderVisit(&a[0],num);
layerPrint(a,n);
return 0;
}
void inOrderVisit(node*p,int* num) //中序遍历填充节点值
{
if(p->left!=-1)
inOrderVisit(&a[p->left],num);
p->data = num[k++];
if(p->right!=-1)
inOrderVisit(&a[p->right],num);
return ;
}
void layerPrint(node a[],int len) //层序遍历打印节点值
{
int count=0;
queue q;
node p;
initQueue(&q);
push(&q,a[0]);
while(q.top!=q.bom)
{
p = pop(&q);
printf("%d",p.data);
count++;
if(count!=len)
putchar(' ');
if(p.left!=-1)
push(&q,a[p.left]);
if(p.right!=-1)
push(&q,a[p.right]);
}
}
int comp(const void* a,const void* b)
{
return *(int*)a -*(int*)b;
}
//队列的相关操作
void initQueue(queue* s)
{
s->top = 0;
s->bom = 0;
}
void push(queue* s,node tmp)
{
s->value[s->top]=tmp;
s->top++;
}
node pop(queue* s)
{
node tmp ;
tmp = s->value[s->bom];
s->bom++;
return tmp;
}
int isEmptyQueue(queue*s)
{
if(s->top==s->bom)
return 1;
return 0;
}