题目：给定一个不含重复元素的整数数组。一个以此数组构建的最大二叉树定义如下：
- 二叉树的根是数组中的最大元素。
- 左子树是通过数组中最大值左边部分构造出的最大二叉树。
- 右子树是通过数组中最大值右边部分构造出的最大二叉树。
通过给定的数组构建最大二叉树，并且输出这个树的根节点。
Example 1:
输入: [3,2,1,6,0,5]
输入: 返回下面这棵树的根节点：
6
/ 3 5
\ /
2 0
1
分析：（1）通过审题可知通过先序创建二叉树进行创建，即创建根节点，左子树，右子数。 所以选择递归的方法进行创建。 visit(T); createleftTree(T->left); creatterightTree(T->right); (2)找数组中的最大值，类似于二分查找， 用三个游标low，high，temp分别来跟踪所要查找的数组中的低位、高位、和最大值的位置。 temp 根节点 [low , temp-1]左子树 [temp+1, high]右子数 （3）根据题意，输出时需要将二叉树按层输出，即按层遍历，使用队列实现，队列的特性FIFO 。（1）根节点入队列-》（2）根节点出队列并输出-》（3）左子树入队列-》（4）右子数入队列-》（3）
定义二叉树结点：typedef struct TreeNode{ int val; struct TreeNode *left; struct TreeNode *right;}TreeNode;定义队列链表结点：typedef struct QNode{ QueuePtr val; QNode *next;}QNode,*QueuePtr;定义队列：typedef struct Queue{ QueuePtr front; QueuePtr rear;}Queue;//Q.front 指向队列链表的头结点； Q.rear 指向队列链表的尾结点；入队列时在Q.rear后加结点，出队列时在Q.front删结点
源代码：/*** Definition for a binary tree node.* struct TreeNode {* int val;* struct TreeNode *left;* struct TreeNode *right;* };*/#include<stdio.h>#include<stdlib.h>
struct TreeNode { int val; struct TreeNode *left; struct TreeNode *right; };//定义链表队列typedef struct QNode { struct TreeNode *val; struct QNode *next;}QNode, *QueuePtr;typedef struct Queue { QueuePtr rear ; //队列尾指针 QueuePtr front; //队列头指针}Queue;// 找出数组中最大的数int searchMaxnum(int *nums, int low, int high, int *location) { int max = -1; int i; i = low; while (i <=high) { if (max< (*(nums + i))) { max = *(nums + i); *location = i; } i++;
} return max;
}void createTree(struct TreeNode** p, int *count, int * nums, int low, int *location, int high) { struct TreeNode* q; int t,max, t_right, t_left;; if (low > high) { return; } if (count == 0) return; max = searchMaxnum(nums, low, high, location); if (max == -1) return; *p = q = (struct TreeNode*)malloc(sizeof(struct TreeNode)); (*p)->val = max; (*p)->left = NULL; (*p)->right = NULL; (*count)--; t_left = (*location) - 1; t_right = (*location) + 1; createTree(&((*p)->left), count, nums, low, location, t_left); createTree(&((*p)->right), count, nums, t_right, location, high);
}
struct TreeNode* constructMaximumBinaryTree(int* nums, int numsSize) { int maxleft, location,t, t_right, t_left; int count = numsSize; int low = 0; int high = numsSize - 1; struct TreeNode* p = NULL; p = (struct TreeNode*)malloc(sizeof(struct TreeNode)); p->val = searchMaxnum(nums, low, high, &location); count--; (p)->left = NULL; (p)->right = NULL; t_left = location-1; t_right = location + 1;
//createTree(&p, searchMaxnum(nums, low, high, &location), &count, nums, &low, &location, &high); createTree(&(p->left), &count, nums, low, &location, t_left); createTree(&(p->right), &count, nums, t_right, &location, high); return p;}//入队列void enqueue(Queue *s, struct TreeNode *t) { QNode *p;
p = (QNode *)malloc(sizeof(QNode)); s->rear->next = p; (s)->rear = p; (s)->rear->val = t; (s)->rear ->next= NULL; }void dequeue(Queue *s, struct TreeNode **t) { QNode *p; (*t) = (s)->front->next->val; p = (s)->front; (s)->front=(s)->front->next; free(p);}void main() { int num[8] = { 3,2,1,6,0,5,10,20}; struct TreeNode* p,*q,*t; //定义树节点 int count = 8; Queue sq; //定义一个队列 t = NULL; struct TreeNode* temp = NULL;//创建最大二叉树 p = constructMaximumBinaryTree(num, count); //printf("%d", p->val); q = p; //head=sq = NULL;// sq->head = sq->rear; //创建队列头结点，为空结点 sq.front = (QueuePtr)malloc(sizeof(QNode)); sq.rear = sq.front; sq.rear->next = NULL; //根节点入队列 if (p != NULL) { enqueue(&sq, p ); } count = 8; //按层遍历二叉树 while ((sq.front)!=(sq.rear)&& count!=0) { dequeue(&sq,&t);
if (t != temp) { printf("%d ", (t)->val); if ((t)->left != NULL) { enqueue(&sq, (t)->left);//左孩子入队列 } else enqueue(&sq, temp); if ((t)->right != NULL) { enqueue(&sq, (t)->right); } else enqueue(&sq, temp); count--; } else printf("null "); }}
原文地址：https://www.cnblogs.com/feifiefighting/p/9069451.html
时间： 2024-10-12 19:00:24