(一)常见排序
import java.util.Arrays;
public class Sort {
//快速排序
private static int partition(int[] arr, int low, int hight) {
int pivotkey = arr[low];
while (low < hight) {
while (low < hight && pivotkey <= arr[hight])
--hight;
int temp1 = arr[low];
arr[low]=arr[hight];
arr[hight]=temp1;
//arr[low] = arr[hight];
while (low < hight && pivotkey >= arr[low])
++low;
int temp2 = arr[low];
arr[low]=arr[hight];
arr[hight]=temp2;
//arr[hight] = arr[low];
}
return low;
}
//快速排序
public static void qSort(int[] arr, int low, int hight) {
if (low < hight) {
int pivotkey = partition(arr, low, hight);
qSort(arr, low, pivotkey - 1);
qSort(arr, pivotkey + 1, hight);
}
}
//插入排序
public static int[] insertOrder(int a[]){
for (int i = 1; i < a.length; i++) {
int k = a[i];
int j;
for (j = i - 1; j >= 0 && k < a[j]; j--) {
a[j + 1] = a[j];
}
a[j + 1] = k;
//System.out.println(Arrays.toString(a));
}
return a;
}
//冒泡排序
public static int[] maopao(int[] a){
for(int i=0;i<a.length-1;i++){//i 代表伦次
for(int j=0;j<a.length-i-1;j++){//j和j+1代表相邻元素
if(a[j]>a[j+1]){
int temp = a[j];
a[j]= a[j+1];
a[j+1]=temp;
}
}
//System.out.println(Arrays.toString(a));
//Arrays.sort(a);
}
return a;
}
//选择排序
public int[] selectOrder(int arr[] ) {
for (int i = 0; i <arr.length; i++) {
int max = arr[i];
for (int j = i + 1; j < arr.length; j++) {
if (arr[j] < max) {
int temp = arr[j];
arr[j] = max;
max = temp;
arr[i] = max;
}
}
}
return arr;
}
// 二分查找
public void binarySearch() {
int b[] = { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16 };
int start = 0;
int end = b.length - 1;
int mid;
int target = 1;
while (true) {
mid = ((end + start) / 2);
if (b[mid] == target) {
System.out.println(mid);
break;
}
if (target < b[mid]) {
end = mid;
}
if (target > b[mid]) {
start = mid + 1;
}
}
}
public static void main(String args[]) {
int Arr[] = { 10, 30, 20, 50, 90, 80, 60, 40, 70 };
System.out.println(Arrays.toString(Arr));
qSort(Arr, 0, Arr.length -1);
System.out.println(Arrays.toString(Arr));
}
}
希尔排序:
算法思想
它是对插入插入排序的改进
搜索维基百科可知
希尔排序,也称递减增量排序算法
假设有这样一组数[ 13 14 94 33 82 25 59 94 65 23 45 27 73 25 39 10 ]
,我们分别以步长为5,3,1进行排序(希尔排序最后的步长一定是1)
步长为5,我们可以得到如下数据,
13 14 94 33 82
25 59 94 65 23
45 27 73 25 39
10
然后 按照列排序
10 14 73 25 23
13 27 94 33 39
25 59 94 65 82
45
将上述四行数字,依序接在一起时我们得到:[ 10 14 73 25 23 13 27 94 33 39 25 59 94 65 82 45 ].这时10已经移至正确位置了,然后再以3为步长进行排序:
10 14 13
25 23 33
27 25 59
39 65 73
45 94 82
94
-最后以1步长进行排序(此时就是简单的插入排序了)。
public static void shellPass(Integer[] array, int d) {
for (int i = d; i < array.length; i++) {
int temp = array[i];
int j = i - d;
while (j >= 0 && array[j] > temp) {
array[j + d] = array[j];
j -= d;
}
array[j + d] = temp;
}
}
public static void shellSort(Integer[] data) {
int increment = 12;
do {
increment = increment / 3 + 1;
shellPass(data, increment);
} while (increment > 1);
}
(二)常见数据结构
2.1 graph
2.1.1图节点
public class GraphNode {
int val;
GraphNode next;
GraphNode[] neighbors;
boolean visited;
GraphNode(int x) {
val = x;
}
GraphNode(int x, GraphNode[] n){
val = x;
neighbors = n;
}
public String toString(){
return "value: "+ this.val;
}
}
2.1.2队列
public class Queue {
GraphNode first, last;
public void enqueue(GraphNode n){
if(first == null){
first = n;
last = first;
}else{
last.next = n;
last = n;
}
}
public GraphNode dequeue(){
if(first == null){
return null;
}else{
GraphNode temp = new GraphNode(first.val, first.neighbors);
first = first.next;
return temp;
}
}
}
2.1.3测试类
public class GraphTest {
public static void main(String[] args) {
GraphNode n1 = new GraphNode(1);
GraphNode n2 = new GraphNode(2);
GraphNode n3 = new GraphNode(3);
GraphNode n4 = new GraphNode(4);
GraphNode n5 = new GraphNode(5);
n1.neighbors = new GraphNode[]{n2,n3,n5};
n2.neighbors = new GraphNode[]{n1,n4};
n3.neighbors = new GraphNode[]{n1,n4,n5};
n4.neighbors = new GraphNode[]{n2,n3,n5};
n5.neighbors = new GraphNode[]{n1,n3,n4};
breathFirstSearch(n1, 5);
}
public static void breathFirstSearch(GraphNode root, int x){
if(root.val == x)
System.out.println("find in root");
Queue queue = new Queue();
root.visited = true;
queue.enqueue(root);
while(queue.first != null){
GraphNode c = (GraphNode) queue.dequeue();
for(GraphNode n: c.neighbors){
if(!n.visited){
System.out.print(n + " ");
n.visited = true;
if(n.val == x)
System.out.println("Find "+n);
queue.enqueue(n);
}
}
}
}
}
2.2link
2.2.1链表实例节点
public class Node {
int val;
Node next;
Node(int x) {
val = x;
next = null;
}
}
2.3Queue
2.3.1队列节点
public class Node {
int val;
Node next;
Node(int x) {
val = x;
next = null;
}
}
2.3.2队列操作类
public class Queue {
Node first, last;
public void enqueue(Node n){
if(first == null){
first = n;
last = first;
}else{
last.next = n;
last = n;
}
}
public Node dequeue(){
if(first == null){
return null;
}else{
Node temp = new Node(first.val);
first = first.next;
return temp;
}
}
}
2.4stack
2.4.1栈的节点
public class Node {
int val;
Node next;
Node(int x) {
val = x;
next = null;
}
}
2.4.2栈的操作类
public class Stack {
Node top;
public Node peek(){
if(top != null){
return top;
}
return null;
}
public Node pop(){
if(top == null){
return null;
}else{
Node temp = new Node(top.val);
top = top.next;
return temp;
}
}
public void push(Node n){
if(n != null){
n.next = top;
top = n;
}
}
}
2.5Tree
2.5.1数的节点
public class TreeNode {
int value;
TreeNode left;
TreeNode right;
}