黑马学习笔记_常用算法复习

public class QuickSort {
// 划分数组
public static int partition(long arr[], int left, int right, long point) {
int leftPtr = left - 1;
int rightPtr = right;
while (true) {
//向后移动索引
while (leftPtr < rightPtr && arr[++leftPtr] < point)
;
//向前移动索引
while (leftPtr < rightPtr && arr[--rightPtr] > point)
;
if (leftPtr >= rightPtr) {
break;
} else {
long temp = arr[leftPtr];
arr[leftPtr] = arr[rightPtr];
arr[rightPtr] = temp;
}
}
long temp = arr[leftPtr];
arr[leftPtr] = arr[right];
arr[right] = temp;
return leftPtr;
}

// 递归实现快速排序
public static void sort(long[] arr, int left, int right) {
if (right <= left) {
return;
} else {
long point = arr[right];
int partition = partition(arr, left, right, point);
sort(arr, left, partition - 1);
sort(arr, partition + 1, right);
}
}
//显示数组
public static void display(long[] arr) {
for (long num : arr) {
System.out.print(num + " ");
}
System.out.println();
}
}

测试类

public class TestSort {
public static void main(String[] args) {
long[] arr=new long[4];
arr[0]=5;
arr[1]=4;
arr[2]=3;
arr[3]=2;
for(long num : arr){
System.out.print(num + " ");
}
//调用快速排序
BubbleSort.sort(arr);
System.out.println();
//遍历显示数组内容
for(long num : arr){
System.out.print(num + " ");
}
}
}

public class Tree {
// 跟节点
public Node root;

// 插入节点
public void insert(long value, String sValue) {
// 封装节点
Node newNode = new Node(value, sValue);
// 引用当前节点
Node current = root;
Node parent = null;
// 判断root为null
if (root == null) {
root = newNode;
return;
} else {
while (true) {
parent = current;
if (value < current.data) {
current = current.leftNode;
if (current == null) {
parent.leftNode = newNode;
return;
}
} else {
current = current.rightNode;
if (current == null) {
parent.rightNode = newNode;
return;
}
}
}
}
}

// 查找节点
public Node find(long value) {
Node current = root;
while (current.data != value) {
if (value < current.data) {
current = current.leftNode;
} else {
current = current.rightNode;
}
if (current == null) {
return null;
}
}
return current;
}

// 前序遍历
public void frontOrder(Node localnode) {
if (localnode != null) {
System.out.println(localnode.data + "---" + localnode.sData);
frontOrder(localnode.leftNode);
frontOrder(localnode.rightNode);
}
}

// 中序遍历
public void inOrder(Node localnode) {
if (localnode != null) {
inOrder(localnode.leftNode);
System.out.println(localnode.data + "," + localnode.sData);
inOrder(localnode.rightNode);
}
}

// 后序遍历
public void afterOrder(Node localnode) {
if (localnode != null) {
afterOrder(localnode.leftNode);
afterOrder(localnode.rightNode);
System.out.println(localnode.data + "," + localnode.sData);
}
}
}

测试类

public class TestTree {
public static void main(String[] args) {
Tree tree = new Tree();
tree.insert(12,"Jamea");
tree.insert(7,"ddd");
tree.insert(20,"Kobi");
tree.insert(30,"my");
tree.insert(10,"Kobi");
tree.insert(3,"my");
//      System.out.println(tree.root.data);
//      System.out.println(tree.root.leftNode.data);
//      Node node = tree.find(30);
//      System.out.println(node.data+","+node.sData);
tree.afterOrder(tree.root);
}
}

刚开始学习算法时候，思路清晰，就是写不出来，后来经常练习渐渐地也就能够把自己思路用代码体现出来了，所以以后我会经常写博客，把自己的想法记录下来，也算是巩固以前学习的知识点了。