C语言解答

#include <stdio.h>

int main(void) {
	int i, j = 0, n, s = 0;
	do
		scanf("%d", &n);
	while(!(n > 0 && n <= 9));
	for(i = 1; i <= n; i ++) {
		j = j * 10 + 1;
		s += i*j;
	}
	printf("%d", s);
	return 0; 
}

C++解答

#include<cstdio>
using namespace std;
int main()
{
    int i,s,n,d;
    scanf("%d",&n);
    s=0;d=0;
    for(i=1;i<=n;i++)
    {
	d=d*10+1;
        s=s+i*d;
    }
    printf("%d",s); 
    return 0; 
}

Python解答

# coding=utf-8
n = input()
print(sum([int(n*i) for i in range(1,int(n)+1)]))