目錄
1 排序算法
2 二分查找
public int binarySearch(int[] array, int target) {
return binarySearch(array, 0, array.length - 1, target);
}
private int binarySearch(int[] array, int left, int right, int target) {
if (left >= right) {
return -1;
}
int mid = left + ((right - left) >>> 1);
if (array[mid] == target) {
return mid;
} else if (array[mid] < target) {
return binarySearch(array, mid + 1, right, target);
} else {
return binarySearch(array, left, mid, target);
}
}
3 鏈表反轉
public class MyLinkedList {
private static class Node {
private int value;
private Node next;
private Node(int value, Node next) {
this.value = value;
this.next = next;
}
@Override
public String toString() {
return Integer.toString(value);
}
}
private Node head;
private void addFirst(int value) {
head = new Node(value, head);
}
public void reverse() {
reverse(head);
}
private Node reverse(Node cur) {
if (cur == null || cur.next == null) {
head = cur;
return cur;
}
Node nextNode = reverse(cur.next);
nextNode.next = cur;
cur.next = null;
return cur;
}
@Override
public String toString() {
StringBuilder stringBuilder = new StringBuilder();
for (Node cur = head; cur != null; cur = cur.next) {
stringBuilder.append(cur).append("->");
}
stringBuilder.append("NULL");
return stringBuilder.toString();
}
public static void main(String[] args) {
MyLinkedList myLinkedList = new MyLinkedList();
Random random = new Random();
for (int i = 0; i < 10; i++) {
myLinkedList.addFirst(random.nextInt(10));
}
System.out.println(myLinkedList);
myLinkedList.reverse();
System.out.println(myLinkedList);
}
}
4 二分搜索樹遍歷
4.1 前序遍歷
public void preOrder() {
preOrder(root);
}
private void preOrder(Node cur) {
if (cur == null) {
return;
}
System.out.print(cur.value + " ");
preOrder(cur.left);
preOrder(cur.right);
}
4.2 中序遍歷
public void inOrder() {
inOrder(root);
}
private void inOrder(Node cur) {
if (cur == null) {
return;
}
inOrder(cur.left);
System.out.print(cur.value + " ");
inOrder(cur.right);
}
4.3 後序遍歷
public void postOrder() {
postOrder(root);
}
private void postOrder(Node cur) {
if (cur == null) {
return;
}
postOrder(cur.left);
postOrder(cur.right);
System.out.print(cur.value + " ");
}
4.4 層序遍歷
public void levelOrder() {
if (root == null) {
return;
}
Queue<Node> queue = new LinkedList<>();
queue.add(root);
while (!queue.isEmpty()) {
Node cur = queue.remove();
System.out.print(cur.value + " ");
if (cur.left != null) {
queue.add(cur.left);
}
if (cur.right != null) {
queue.add(cur.right);
}
}
}
5 斐波那契數列
public int fibonacci(int index) {
if (index == 1 || index == 2) {
return 1;
} else {
return fibonacci(index - 1) + fibonacci(index - 2);
}
}
6 判斷鏈表是否有環
設置兩個快慢指針，一個步長爲1，另一個步長爲2。如果兩個指針最終相遇則說明鏈表有環：
public boolean isLoop() {
if (head == null || head.next == null) {
return false;
}
Node fast = head;
Node slow = head;
while (fast.next != null && fast.next.next != null) {
fast = fast.next.next;
slow = slow.next;
if (fast == slow) {
return true;
}
}
return false;
}
7 使用阻塞隊列來實現一個生產者消費者模型
import java.util.concurrent.BlockingQueue;
public class Producer implements Runnable {
private final BlockingQueue blockingQueue;
public Producer(BlockingQueue blockingQueue) {
this.blockingQueue = blockingQueue;
}
@Override
public void run() {
for (int i = 0; i < 10; i++) {
System.out.println("produced:" + i);
try {
blockingQueue.put(i);
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}
}
import java.util.concurrent.BlockingQueue;
public class Consumer implements Runnable {
private final BlockingQueue blockingQueue;
public Consumer(BlockingQueue blockingQueue) {
this.blockingQueue = blockingQueue;
}
@Override
public void run() {
while (true) {
try {
System.out.println("consumed:" + blockingQueue.take());
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}
}
import java.util.concurrent.BlockingQueue;
import java.util.concurrent.LinkedBlockingQueue;
public class ProducerConsumerTest {
public static void main(String[] args) {
BlockingQueue blockingQueue = new LinkedBlockingQueue();
Thread producerThread = new Thread(new Producer(blockingQueue));
Thread consumerThread = new Thread(new Consumer(blockingQueue));
producerThread.start();
consumerThread.start();
}
}