Question

用控制台应用程序编写计算9+99+999+...+9999999999的值

Answer 1

static void Main(string[] args)
{
Console.WriteLine(9L + 99L + 999L + 9999L +
99999L + 999999L + 9999999L +
99999999L + 999999999L + 9999999999L);
}

Answer 2

public static void main(String[] args) {

long n=0L,sum=0;
while(n<=999999999) {
n=n*10+9;
sum=sum+n;
if(n<=999999999)System.out.print(n+"+");
else System.out.print(n);
}
System.out.print("=");
System.out.println(sum);
}