#A + B 问题
##A + B 问题 I
创建class， 创建main函数， Scanner用法
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| import java.util.*;
public class Main{
public static void main(String[] args){
Scanner sc = new Scanner(System.in);
while (sc.hasNextInt()){
int a = sc.nextInt();
int b = sc.nextInt();
System.out.println(a + b);
}
sc.close();
}
}
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##A + B 问题 II
for循环， while循环， ++ 和 –；
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import java.util.*;
class Main{
public static void main(String[] args){
Scanner sc = new Scanner(System.in);
while(sc.hasNextInt()){
int n = sc.nextInt();
for (int i = 0; i < n ;i++){
int a = sc.nextInt();
int b = sc.nextInt();
System.out.println(a + b);
}
}
sc.close();
}
}
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##A + B 问题 III
if 语句，关系运算，break退出
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| import java.util.*;
class Main{
public static void main(String[] args){
Scanner sc = new Scanner(System.in);
while (sc.hasNextInt()){
int a = sc.nextInt();
int b = sc.nextInt();
if (a == 0 && b == 0){
break;
} else {
System.out.println(a + b);
}
}
sc.close();
}
}
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##A + B 问题 IV
累加运算，算术运算， 赋值运算，三元运算
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| import java.util.*;
public class Main{
public static void main(String[] args) {
Scanner sc = new Scanner(System.in);
while (sc.hasNextInt()){
int n = sc.nextInt();
if (n == 0){
break;
}
int sum = 0;
while (n-- > 0){
sum += sc.nextInt();
}
System.out.println(sum);
}
sc.close();
}
}
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##A + B 问题 VIII
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| import java.util.*;
public class Main{
public static void main(String[] args){
Scanner sc = new Scanner(System.in);
while (sc.hasNextInt()){
int n = sc.nextInt();
sc.nextLine();
while (n-- > 0){
int m = sc.nextInt();
int sum = 0;
while (m-- > 0){
sum += sc.nextInt();
}
System.out.println(sum);
if (n != 0) System.out.println();
}
}
}
}
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#倒序输出数组与隔位输出
##fix length 数组
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| import java.util.*;
public class Main{
public static void main(String[] args){
Scanner sc = new Scanner(System.in);
while (sc.hasNextInt()){
int n = sc.nextInt();
int[] record = new int[n];
for (int i = 0; i < n; i++){
record[i] = sc.nextInt();
}
for(int i = n - 1; i >= 0; i--){
System.out.print(record[i] + " ");
}
System.out.println();
for (int i = 0; i < n; i += 2){
System.out.print(record[i] + " ");
}
}
sc.close();
}
}
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##ArrayList 实现
ArrayList 方法
添加：.add()
查找：.get(index)
长度：.size()
删除：.remove(index)
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| import java.util.*;
public class Main{
public static void main(String[] args){
Scanner sc = new Scanner(System.in);
while (sc.hasNextInt()){
int n = sc.nextInt();
List<Integer> record = new ArrayList<>();
for (int i = 0; i < n; i++){
record.add(sc.nextInt());
}
for(int i = record.size() - 1; i >= 0; i--){
System.out.print(record.get(i) + " ");
}
System.out.println();
for (int i = 0; i < record.size(); i += 2){
System.out.print(record.get(i) + " ");
}
}
sc.close();
}
}
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摆平积木
算average的方法
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| import java.util.*;
public class Main{
public static void main(String[] args){
Scanner sc = new Scanner(System.in);
while (sc.hasNextInt()){
int n = sc.nextInt();
if (n == 0){
break;
}
List<Integer> record = new ArrayList<>();
int sum = 0;
int m = n;
while (m-- > 0){
int temp = sc.nextInt();
record.add(temp);
sum += temp;
}
int recordAvg = sum / n;
int result = 0;
for (int i = 0; i < n; i++){
if (record.get(i) > recordAvg){
result += record.get(i) - recordAvg;
}
}
System.out.println(result);
System.out.println();
}
}
}
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奇怪的信
找到int中每个数字的做法
n % 10 找到数字
n /= 10 除去数字
n % 2 判断奇偶数
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| import java.util.*;
public class Main{
public static void main(String[] args){
Scanner sc = new Scanner(System.in);
while (sc.hasNextInt()){
int n = sc.nextInt();
int sum = 0;
while (n > 0){
int temp = n % 10;
if (temp % 2 == 0){
sum += temp;
}
n/=10;
}
System.out.println(sum);
System.out.println();
}
}
}
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打印正方形
简单的模拟题
设置result[][] 数组，检查填充，再打印
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| import java.util.*;
public class Main{
public static void main(String[] args){
Scanner sc = new Scanner(System.in);
int n = sc.nextInt();
char[][] result = new char[n][n];
for (int i = 0; i < n; i++){
for (int j = 0; j < n; j++){
if (i == 0 || j == 0 || i == n- 1 || j == n -1 ){
result[i][j] = '*';
} else {
result[i][j] = ' ';
}
}
}
for (int i = 0; i < n; i++){
for (int j = 0; j < n; j++){
System.out.print(result[i][j]);
}
System.out.println();
}
}
}
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平均绩点
String的用法
长度：.length();
比较：.equals();
切割拆分：.split();
索引：.charAt(index);
替换：.replace()
查找：.indexOf(子串)；
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|
import java.util.*;
public class Main{
public static void main(String[] args){
Scanner sc = new Scanner(System.in);
while (sc.hasNextLine()){
String[] n = sc.nextLine().split(" ");
int sum = 0, count = 0;
int flag = 0;
for (int i = 0; i < n.length; i++){
if (n[i].equals("A")){
sum += 4;
count++;
} else if (n[i].equals("B")){
sum += 3;
count++;
} else if (n[i].equals("C")){
sum += 2;
count++;
} else if (n[i].equals("D")){
sum += 1;
count++;
} else if (n[i].equals("F")){
sum += 0;
count++;
} else {
flag = 1;
}
}
if (flag == 1){
System.out.println("Unknown");
} else {
System.out.printf("%.2f", (double) sum / count);
System.out.println();
}
}
}
}
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句子缩写
Character.toUpperCase()
Character.toLowerCase();
String.trim() delete extra space
延伸删除额外的space的写法
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import java.util.*;
public class Main{
public static void main(String[] args){
Scanner sc = new Scanner(System.in);
while (sc.hasNextInt()){
int n = sc.nextInt();
sc.nextLine();
while (n-- > 0){
String result = removeExtraSpaces(sc.nextLine());
StringBuilder sb = new StringBuilder();
int i = 0;
sb.append(Character.toUpperCase(result.charAt(0)));
while (i < result.length()){
if (result.charAt(i) == ' '){
sb.append(Character.toUpperCase(result.charAt(i + 1)));
}
i++;
}
System.out.println(sb);
}
}
}
private static String removeExtraSpaces(String s){
int left = 0;
int right = s.length() - 1;
while (left < s.length() && s.charAt(left) == ' ') left++;
while (right >= 0 && s.charAt(right) == ' ') right--;
StringBuilder sb = new StringBuilder();
while (left <= right){
if(s.charAt(left) != ' ' || sb.charAt(sb.length()-1) != ' '){
sb.append(s.charAt(left));
}
left++;
}
return sb.toString();
}
}
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位置互换
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| import java.util.*;
public class Main{
public static void main(String[] args){
Scanner sc = new Scanner(System.in);
while (sc.hasNextInt()){
int n = sc.nextInt();
sc.nextLine();
while (n-- > 0){
String s = sc.nextLine();
char[] str = s.toCharArray();
int i = 0;
while (i < s.length()){
swapInArray(str, i, i+1);
i += 2;
}
System.out.println(new String(str));
}
}
}
private static void swapInArray(char[] str, int m, int n){
str[m] ^= str[n];
str[n] ^= str[m];
str[m] ^= str[n];
}
}
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