Java基础23-递归练习
Created At :
Count:2.3k
Views 👀 :
public class Test1 {
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
| public class Test1 {
public static void main(String[] args) {
File dir = getDir();
System.out.println(getFileLength(dir));
}
public static File getDir() {
Scanner sc = new Scanner(System.in);
System.out.println("请输入一个文件夹路径:");
while(true) {
String line = sc.nextLine();
File dir = new File(line);
if(!dir.exists()) {
System.out.println("您录入的文件夹路径不存在,请输入一个文件夹路径:");
}else if(dir.isFile()) {
System.out.println("您录入的是文件路径,请输入一个文件夹路径:");
}else {
return dir;
}
}
}
public static long getFileLength(File dir) {
long len = 0;
File[] subFiles = dir.listFiles();
for (File subFile : subFiles) {
if(subFile.isFile()) {
len = len + subFile.length();
}else {
len = len + getFileLength(subFile);
}
}
return len;
}
}
|
Test2
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
| public class Test2 {
public static void main(String[] args) {
File dir = Test1.getDir();
deleteFile(dir);
}
public static void deleteFile(File dir) {
File[] subFiles = dir.listFiles();
for (File subFile : subFiles) {
if(subFile.isFile()) {
subFile.delete();
}else {
deleteFile(subFile);
}
}
dir.delete();
}
}
|
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
| public class Test3 {
public static void main(String[] args) throws IOException {
File src = Test1.getDir();
File dest = Test1.getDir();
if(src.equals(dest)) {
System.out.println("目标文件夹是源文件夹的子文件夹");
}else {
copy(src,dest);
}
}
public static void copy(File src, File dest) throws IOException {
File newDir = new File(dest, src.getName());
newDir.mkdir();
File[] subFiles = src.listFiles();
for (File subFile : subFiles) {
if(subFile.isFile()) {
BufferedInputStream bis = new BufferedInputStream(new FileInputStream(subFile));
BufferedOutputStream bos =
new BufferedOutputStream(new FileOutputStream(new File(newDir,subFile.getName())));
int b;
while((b = bis.read()) != -1) {
bos.write(b);
}
bis.close();
bos.close();
}else {
copy(subFile,newDir);
}
}
}
}
|
Test4
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
| public class Test4 {
public static void main(String[] args) {
File dir = Test1.getDir();
printLev(dir,0);
}
public static void printLev(File dir,int lev) {
File[] subFiles = dir.listFiles();
for (File subFile : subFiles) {
for(int i = 0; i <= lev; i++) {
System.out.print("\t");
}
System.out.println(subFile);
if(subFile.isDirectory()) {
printLev(subFile,++lev);
}
}
}
}
|
Test5
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
| public class Test5 {
public static void main(String[] args) {
System.out.println(fun(8));
}
public static void demo1() {
int[] arr = new int[8];
arr[0] = 1;
arr[1] = 1;
for(int i = 2; i < arr.length; i++) {
arr[i] = arr[i - 2] + arr[i - 1];
}
System.out.println(arr[arr.length - 1]);
}
public static int fun(int num) {
if(num == 1 || num == 2) {
return 1;
}else {
return fun(num - 2) + fun(num - 1);
}
}
}
|
Test6
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
| public class Test6 {
public static void main(String[] args) {
demo2();
}
public static void demo2() {
BigInteger bi1 = new BigInteger("1");
for(int i = 1; i <= 1000; i++) {
BigInteger bi2 = new BigInteger(i+"");
bi1 = bi1.multiply(bi2);
}
String str = bi1.toString();
StringBuilder sb = new StringBuilder(str);
str = sb.reverse().toString();
int count = 0;
for(int i = 0; i < str.length(); i++) {
if('0' != str.charAt(i)) {
break;
}else {
count++;
}
}
System.out.println(count);
}
public static void demo1() {
BigInteger bi1 = new BigInteger("1");
for(int i = 1; i <= 1000; i++) {
BigInteger bi2 = new BigInteger(i+"");
bi1 = bi1.multiply(bi2);
}
String str = bi1.toString();
int count = 0;
for(int i = 0; i < str.length(); i++) {
if('0' == str.charAt(i)) {
count++;
}
}
System.out.println(count);
}
}
|
Test7
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
| public class Test7 {
public static void main(String[] args) {
System.out.println(fun(1000));
}
public static int fun(int num) {
if(num > 0 && num < 5) {
return 0;
}else {
return num / 5 + fun(num / 5);
}
}
}
|
Test8
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
| public class Test8 {
public static void main(String[] args) {
System.out.println(getLucklyNum(8));
}
public static int getLucklyNum(int num) {
ArrayList<Integer> list = new ArrayList<>();
for(int i = 1; i <= num; i++) {
list.add(i);
}
int count = 1;
for(int i = 0; list.size() != 1; i++) {
if(i == list.size()) {
i = 0;
}
if(count % 3 == 0) {
list.remove(i--);
}
count++;
}
return list.get(0);
}
}
|
转载请注明来源，欢迎对文章中的引用来源进行考证，欢迎指出任何有错误或不够清晰的表达。可以在下面评论区评论，也可以邮件至 1210331079@qq.com
Title:Java基础23-递归练习
Count:2.3k
Author:千 羽
Created At:2020-06-16, 12:21:56
Updated At:2020-11-27, 09:02:29
Url:https://nateshao.github.io/2020/06/16/Java%E5%9F%BA%E7%A1%8023-%E9%80%92%E5%BD%92%E7%BB%83%E4%B9%A0/
Copyright: 'Attribution-non-commercial-shared in the same way 4.0' Reprint please keep the original link and author.
