k = $k;        $this->left = $left;        $this->right = $right;    }        public function isEmpty(){        return !isset($this->k);    }        public function getKey(){        return isset($this->k) ? $this->k : false;    }        public function setKey($k){                if(!$this->isEmpty())            return ;        $this->k = $k;        $this->left = new Tree();        $this->right = new Tree();        return true;    }        public function deleteKey(){        if(!$this->isLeaf())            return false;        $ret  = $this->k;        $this->k = null;        $this->left = null;        $this->right = null;        return $ret;    }        public function setLeftKey( Tree $obj){        if( $this->left || !$this->left->isEmpty())            return false;        $this->left = $obj;    }        public function delLeftKey(){            if($this->isEmpty())            return;        $ret = $this->left ;        $this->left = new Tree();        return $ret;    }            public function setRightKey( Tree $obj){        if( $this->left || !$this->left->isEmpty())            return false;        $this->left = $obj;    }        public function delRightKey(){            if($this->isEmpty())            return;        $ret = $this->left ;        $this->left = new Tree();        return $ret;    }        }/** * 二叉树排序 * @author: xiaojiang  * */class bTree extends Tree{        static public function initbTree($array){                $root = new bTree();        foreach($array as $val){            $root->insert($val);        }        return $root;    }        public function compare($obj){        return $this->k - $obj;        }        public function contain($obj){            if ($this->isEmpty())            return false;        $diff = $this->compare($obj);        if($diff == 0){            return true;        }else if($diff > 0){            return $this->right->contain($obj);        }else {            return $this->left->contain($obj);        }    }        public function insert($obj){                if($this->isEmpty()){            $this->setKey($obj);        }else{            $diff = $this->compare($obj);            if($diff > 0){                $this->left->insert($obj);            }else{                $this->right->insert($obj);            }        }        $this->_afterInsert();    }        public function findMax(){        if($this->isEmpty())            return;        if(!$this->right->isEmpty())            return $this->right->findMax();        else                 return $this->k;    }        public function findMin(){            if($this->isEmpty())            return ;        if(!$this->left->isEmpty())            return $this->left->findMin();        else             return $this->k;    }        public function setKey($k){                if(!$this->isEmpty())            return ;        $this->k = $k;        $this->left = new bTree();        $this->right = new bTree();        return true;    }        protected function _afterInsert(){}}$arr = array(1,5,4,5,10);$btree = bTree::initbTree($arr);echo $btree->findMax();    // 10 echo "
";echo $btree->findMin();   // 1

 

非常适用于多数字排序。。避免了批量循环的重复判断···