package day02;
import java.util.Arrays;
import java.util.Scanner;
public class homework2 {
public static void main(String[] args) {
//1. for循环:计算 7+77+777+…… 前10项的值
long sum=0;
long m=0;
for(int i=1;i<=10;i++){
m=m*10+7;
sum=sum+m;
}
System.out.println("7+77+777+…… 前10项的值:"+sum);
System.out.println(m);
// 2. for循环:计算序列的值:1,-2,3,-4,5,-6……-100
Scanner ss =new Scanner(System.in);
int[] list=new int [100];
int su=0;
for(int i=1;i<=100;i++){
if(i%2==0){
list[i-1]=-i;
su-=i;
}else{
list[i-1]=i;
su+=i;
}
}
System.out.println(Arrays.toString(list));
System.out.println("前100项和为:"+su);
System.out.println("请输入要查找index:");
int s=ss.nextInt();
System.out.println("第"+s+"项为:"+list[s-1]);
// 3. 打印九九乘法表(两层for循环)
for(int i=1;i<=9;i++){
for(int j =1;j<=i; j++){
System.out.print(j+"*"+i+"="+i*j+"\t");
}
System.out.println();
}
}
}
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