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母牛的故事
import java.util.Scanner;
public class Main {
public static void main(String[] args) {
Scanner in=new Scanner(System.in);
int n=in.nextInt();
while (n>0&&n<55) {
System.out.println(f(n));
n=in.nextInt();
}
}
private static int f(int n) {
if (n==0) {
return 0;
}
if (n==1) {
return 1;
}
if (n==2) {
return 2;
}
if (n==3) {
return 3;
}
return f(n-1)+f(n-3);
}
}
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Hello,World!
import java.util.Scanner;
public class Main {
public static void main(String[] args) {
Scanner in=new Scanner(System.in);
int n;
while (in.hasNext()) {
n=in.nextInt();
System.out.print((char)n);
}
}
}
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用筛法求之N内的素数
import java.util.Scanner;
public class Main {
public static void main(String[] args) {
Scanner in=new Scanner(System.in);
int n=in.nextInt();
boolean[] notPrime=new boolean[n];
for (int i = 2; i < n; i++) {
if (!notPrime[i]) {
System.out.println(i);
for (int j = 2; j*i < n; j++) {
notPrime[i*j]=true;
}
}
}
}
}
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字符逆序
import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
import java.util.Scanner;
public class Main {
public static void main(String[] args) {
Scanner in=new Scanner(System.in);
String string=in.nextLine();
List<Character> list=new ArrayList<>();
for (int i = 0; i < string.length(); i++) {
list.add(string.charAt(i));
}
Collections.reverse(list);
for (Character c : list) {
char ch=c;
System.out.print(ch);
}
}
}
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字符串的输入输出处理
import java.util.Scanner;
public class Main {
public static void main(String[] args) {
Scanner in=new Scanner(System.in);
int n=in.nextInt();
String s1=in.nextLine();
while (n>0) {
s1=in.nextLine();
System.out.println(s1);
System.out.println();
n--;
}
String s2;
while (in.hasNext()) {
s2=in.next();
System.out.println(s2);
System.out.println();
}
}
}
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The 3n+1 Problem
import java.util.Scanner;
public class Main {
public static void main(String[] args) {
Scanner in=new Scanner(System.in);
while (in.hasNext()) {
int n=in.nextInt();
int m=in.nextInt();
System.out.print(n+" "+m+" ");
int max=0;
for (int j = Math.min(n, m); j <= Math.max(n, m); j++) {
int i=1;
int k=j;
while (k!=1&&(k>0&&k<1000000)) {
if (k%2==0) {
k/=2;
}else {
k=k*3+1;
}
i++;
}
max=Math.max(i, max);
}
System.out.println(max);
}
}
}
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Minesweeper扫雷
import java.util.Scanner;
public class Main {
public static void main(String[] args) {
Scanner in=new Scanner(System.in);
int n=in.nextInt();
int m=in.nextInt();
String s=in.nextLine();//读取回车符，下同
int c=1;//判断雷的数量
while (in.hasNext()&&(n!=0||m!=0)) {
char[][] a=new char[n+2][m+2];//增加两行两列，便于判断雷的数量，防止数组越界
for (int i = 0; i < n+2; i++) {
if (i!=0&&i!=n+1) {
s=in.nextLine();
}
for (int j = 0; j < m+2; j++) {
if (i==0||i==n+1||j==0||j==m+1) {
a[i][j]='.';
}else {
a[i][j]=s.charAt(j-1);
}
}
}
for (int i = 1; i < n+1; i++) {
for (int j = 1; j < m+1; j++) {
if (a[i][j]=='*') {
continue;
}else {
int num=0;
for (int k = i-1; k <= i+1; k++) {
for (int l = j-1; l <= j+1; l++) {
if (k==i&&l==j) {
continue;
}else if(a[k][l]=='*'){
num++;
}
}
}
a[i][j]=(char)(num+48);
}
}
}
System.out.println("Field #"+c+":");
for (int i = 1; i < n+1; i++) {
for (int j = 1; j < m+1; j++) {
System.out.print(a[i][j]);
}
System.out.println();
}
System.out.println();
n=in.nextInt();
m=in.nextInt();
s=in.nextLine();
c++;
}
}
}