二叉查找树(Binary Search Tree),也称有序二叉树(ordered binary tree),排序二叉树(sorted binary tree),是指一棵空树或者具有下列性质的二叉树:
1. 若任意节点的左子树不空,则左子树上所有结点的值均小于它的根结点的值;
2. 若任意节点的右子树不空,则右子树上所有结点的值均大于它的根结点的值;
3. 任意节点的左、右子树也分别为二叉查找树;
4. 没有键值相等的节点;
本文跟前文一样只是实现了增加和查找功能,需要一个节点辅助类:
@interface BinaryNode:NSObject @property (strong,nonatomic) NSString *key;//键 @property (strong,nonatomic) NSString *value;//值 @property (strong,nonatomic) BinaryNode *left;//左子树的节点 @property (strong,nonatomic) BinaryNode *right;//右子树的节点 @property (assign,nonatomic) NSInteger childCount;//以该结点为根的自述中的结点总数 -(void)initWithData:(NSString *)key value:(NSString *)value childCount:(NSInteger)childCount; @end
BinaryNode实现代码:
@implementation BinaryNode -(void)initWithData:(NSString *)key value:(NSString *)value childCount:(NSInteger)childCount{ self.key=key; self.value=value; self.childCount=childCount; } @end
二叉查找树需要顶一个一个根结点:
@interface BinarySearchTree : NSObject @property (strong,nonatomic) BinaryNode *root;//二叉平衡树的根节点 -(NSString *)get:(NSString *)key;//获取键对应的值 -(void)put:(NSString *)key value:(NSString *)value;//插入键值对 @end
实现代码:
@implementation BinarySearchTree -(NSString *)get:(NSString *)key{ return [self getByKey:self.root key:key]; } -(NSString *)getByKey:(BinaryNode *)node key:(NSString *)key{ //在node为根结点的子树种查找并返回key所对应的值 //如果找不到返回null if (node==nil) { return nil; } //左右节点进行比较,每个结点的键值大于左子树的结点值小于右子树的结点值 NSInteger compare=[key integerValue]-[node.key integerValue]; if (compare>0) { return [self getByKey:node.right key:key]; }else if(compare<0){ return [self getByKey:node.left key:key]; }else{ return node.value; } } //http://www.cnblogs.com/xiaofeixiang -(void)put:(NSString *)key value:(NSString *)value{ //查找键值,找到则更新它的值,否则为它创建一个新的结点 self.root=[self putNode:self.root key:key value:value]; } -(BinaryNode *)putNode:(BinaryNode *)node key:(NSString *)key value:(NSString *)value{ if (node==nil) { BinaryNode *newNode=[[BinaryNode alloc]init]; [newNode initWithData:key value:value childCount:1]; return newNode; } NSInteger compare=[key integerValue]-[node.key integerValue]; if (compare>0) { node.right=[self putNode:node.right key:key value:value]; }else if(compare<0){ node.left=[self putNode:node.left key:key value:value]; }else{ node.value=value; } node.childCount=[self childSizeCount:node.left]+[self childSizeCount:node.right]+1; return node; } -(NSInteger)childSize{ return [self childSizeCount:self.root]; } -(NSInteger)childSizeCount:(BinaryNode *)node{ if (node==nil) { return 0; }else{ return node.childCount; } } @end
测试:
BinarySearchTree *binaryTree=[[BinarySearchTree alloc]init]; [binaryTree put:@"3" value:@"FlyElephant"]; [binaryTree put:@"9" value:@"http://www.cnblogs.com/xiaofeixiang"]; [binaryTree put:@"10" value:@"博客园"]; [binaryTree put:@"0" value:@"228407086"]; NSString *temp=[binaryTree get:@"9"]; NSLog(@"二叉查找树:%@",temp);
效果如下:
时间: 2024-10-15 19:10:45