当我有一个包含{3,2,6,7,...,99}等100个元素的数组列表时，如何制作BST？
答案 0 :(得分：8)
我相信TreeSet是二叉搜索树的实现。由于整数具有自然排序，因此您可以简单地遍历整数数组并将它们全部添加到TreeSet<Integer>。
另请注意，有一个方法Arrays.binarySearch可以在排序数组中进行二进制搜索。
int[] someInts = {3,2,6,7, /*...,*/ 99};
// use a TreeSet
TreeSet<Integer> ints = new TreeSet<Integer>();
for (int i : someInts)
ints.add(i);
System.out.println(ints.contains(2)); // true
System.out.println(ints.contains(5)); // false
// or sort the array and use Arrays.binarySearch
Arrays.sort(someInts);
System.out.println(Arrays.binarySearch(someInts, 2) >= 0); // true
System.out.println(Arrays.binarySearch(someInts, 5) >= 0); // false
答案 1 :(得分：1)
答案 2 :(得分：1)
除非您想自己实现所有内容（在这种情况下，您可能需要检查here），您应该查看[Collections.binarySearch] [2]。
[2]：http://download.oracle.com/javase/1.4.2/docs/api/java/util/Collections.html#binarySearch(java.util.List，java.lang.Object）
答案 3 :(得分：1)
答案 4 :(得分：1)
我最近完成了一个我们基本上必须这样做的项目。
你可以看看这个课程
编辑：这是用C ++编写的，我看到你用Java编写代码，我很抱歉！
/**************************************
* Tree.cpp - Created by DT
**************************************
*
* Functions:
*
* public:
* Tree();
* void addNode(int);
* bool findID(int);
* Node* findNode(int);
* Node* findParent(int);
* bool deleteID(int);
* Node* findMaximum(Node*);
* Node* findMinimum(Node*);
* void printInOrder();
* void printPreOrder();
* void printPostOrder();
* int recurseHeight(Node*);
* int getHeight();
* void inOrder(Node*);
* void preOrder(Node*);
* void postOrder(Node*);
*
***************************************/
#include <iostream>
#include "Node.h"
#include "Tree.h"
using namespace std;
Tree::Tree() {
root = NULL;
}
///////////////////////////////
// AddNode Function:
///////////////////////////////
void Tree::addNode(int id) {
if(findNode(id)) {
cout << "This ID already exists in the tree" << endl;
return;
}
//if(id == 2147483647) {
// cout << "Overflow Detected: Did you enter a really big number?\n";
// cout << "This ID is being stored as 2147483647\n";
//}
Node *newNode = new Node();
newNode->id = id;
if(root == NULL) {
root = newNode;
return;
}
Node *nextNode = root;
Node *lastNode = nextNode;
while(nextNode != NULL) {
if(id <= nextNode->id) {
lastNode = nextNode;
nextNode = nextNode->leftChild;
}
else {
lastNode = nextNode;
nextNode = nextNode->rightChild;
}
}
if(id <= lastNode->id)
lastNode->leftChild = newNode;
else
lastNode->rightChild = newNode;
}
///////////////////////////////
// FindID Function:
///////////////////////////////
bool Tree::findID(int id) {
Node *finder = root;
while(finder != NULL) {
if(id == finder->id)
return true;
if(id <= finder->id)
finder = finder->leftChild;
else
finder = finder->rightChild;
}
return false;
}
///////////////////////////////
// FindNode Helper Function:
///////////////////////////////
Node* Tree::findNode(int id) {
Node *finder = root;
while(finder != NULL) {
if(id == finder->id)
return finder;
if(id <= finder->id)
finder = finder->leftChild;
else
finder = finder->rightChild;
}
return NULL;
}
///////////////////////////////
// FindParent Helper Function:
///////////////////////////////
Node* Tree::findParent(int id) {
Node *parent = NULL;
Node *finder = root;
while(finder != NULL) {
if(id == finder->id)
return parent;
parent = finder;
if(id <= finder->id)
finder = finder->leftChild;
else
finder = finder->rightChild;
}
return NULL;
}
///////////////////////////////
// DeleteID Function:
///////////////////////////////
bool Tree::deleteID(int id) {
if(root == NULL)
return false;
Node *toDelete = findNode(id); //Find the node to delete
if(toDelete == NULL) //If we can't find it, return false
return false;
Node *parent = findParent(id); //Find the parent of the node to delete
Node *justInCase; //In case we are deleting the root node
bool deletingRoot = false; //This is a special case so handle it differently
if(root->id == id) { //If we're deleting the root node
justInCase = new Node(); //Let's create a fake parent for the root
justInCase->leftChild = root; //Just to make sure that we can run checks on parents
justInCase->rightChild = NULL;
justInCase->id = 0; //Later on in the code
parent = justInCase; //Set the parent of the root to our new fake node
deletingRoot = true; //Let the end of our function know we're deleting the root
}
bool deletingLeftChild = (parent->leftChild == toDelete);
if(toDelete->leftChild == NULL && toDelete->rightChild == NULL) {
if(toDelete == root)
root = NULL;
if(deletingLeftChild)
parent->leftChild = NULL;
else
parent->rightChild = NULL;
delete toDelete;
return true;
}
if((toDelete->leftChild == NULL || toDelete->rightChild == NULL) && (parent != NULL && !deletingRoot)) {
if(deletingLeftChild)
parent->leftChild = (toDelete->leftChild == NULL) ? toDelete->rightChild : toDelete->leftChild;
else
parent->rightChild = (toDelete->leftChild == NULL) ? toDelete->rightChild : toDelete->leftChild;
delete toDelete;
return true;
}
Node *replacer = findMaximum(toDelete->leftChild); //Replace the node we're deleting with the hightest LEFT Child
if(replacer == NULL || replacer == toDelete) //If we can't find a left child (in case of deleting root)
replacer = findMinimum(toDelete->rightChild); //Find the smallest RIGHT child
Node *replacerParent = findParent(replacer->id); //Find the parent of this child
if(replacerParent != NULL) { //If this child has a parent
if(replacerParent->leftChild == replacer) { //If the child is to the left of the parent
if(replacer->leftChild != NULL) //And the left child has a child of its own (in case of findMinimum/maximum)
replacerParent->leftChild = replacer->leftChild;//set the parent's child to this child's node
else
replacerParent->leftChild = NULL; //Otherwise, set the parent's child to NULL
}
else { //In the case of Right Child
if(replacer->rightChild != NULL) //Do the same thing
replacerParent->rightChild = replacer->rightChild;
else
replacerParent->rightChild = NULL;
}
}
toDelete->id = replacer->id; //Swap the IDs of the nodes we're deleting
delete replacer; //And delete the minimum or maximum that we found
return true;
}
///////////////////////////////
// FindMaximum Helper Function:
///////////////////////////////
Node* Tree::findMaximum(Node *theNode) {
if(theNode == NULL)
return NULL;
Node *finder = theNode;
Node *last = finder;
while(finder != NULL) {
last = finder;
finder = finder->rightChild;
}
return last;
}
///////////////////////////////
// FindMinimum Helper Function:
///////////////////////////////
Node* Tree::findMinimum(Node *theNode) {
if(theNode == NULL)
return NULL;
Node *finder = theNode;
Node *last = finder;
while(finder != NULL) {
last = finder;
finder = finder->leftChild;
}
return last;
}
///////////////////////////////
// PrintInOrder Function:
///////////////////////////////
void Tree::printInOrder() {
inOrder(root); //Recurse through our root
cout << "\b " << endl;
}
///////////////////////////////
// PrintPostOrder Function:
///////////////////////////////
void Tree::printPostOrder() {
postOrder(root); //Recurse through our root
cout << "\b " << endl;
}
///////////////////////////////
// PrintPreOrder Function:
///////////////////////////////
void Tree::printPreOrder() {
preOrder(root); //Recurse through our root
cout << "\b " << endl;
}
///////////////////////////////
// RecurseHeight Function:
///////////////////////////////
int Tree::recurseHeight(Node *node) {
if(node == NULL) return -1;
return 1 + max(recurseHeight(node->leftChild),recurseHeight(node->rightChild));
}
///////////////////////////////
// GetHeight Function:
///////////////////////////////
int Tree::getHeight() { return recurseHeight(root); } //Recurse through our root
///////////////////////////////
// InOrder Function:
///////////////////////////////
void Tree::inOrder(Node *cNode) {
if(cNode == NULL)
return;
inOrder(cNode->leftChild);
cout << cNode->id << "-";
inOrder(cNode->rightChild);
}
///////////////////////////////
// PostOrder Function:
///////////////////////////////
void Tree::postOrder(Node *cNode) {
if(cNode == NULL)
return;
postOrder(cNode->leftChild);
postOrder(cNode->rightChild);
cout << cNode->id << "-";
}
///////////////////////////////
// PreOrder Function:
///////////////////////////////
void Tree::preOrder(Node *cNode) {
if(cNode == NULL)
return;
cout << cNode->id << "-";
preOrder(cNode->leftChild);
preOrder(cNode->rightChild);
}
节点类：
/**************************************
* Node.cpp - Created by DT
**************************************
*
* An incredibly simple class that
* apparently deserves its own header
*
***************************************/
#include "Node.h"
#include <iostream>
Node::Node() {
leftChild = NULL;
rightChild = NULL;
id = NULL;
}