[백준] 1748번 : 수 이어 쓰기1 - C

https://www.acmicpc.net/problem/1748

#include<stdio.h>
#include <string.h>
static int zero(int n){
    int z=1;
    if(n<=0) z=0;
    else{
        for(int i=1;i<=n-1;i++){
            z*=10;
        }
    }
    return z;
}

int main() {
    int n;
    scanf("%d",&n);
    char k[15];
    sprintf(k,"%d",n);
    int len=strlen(k);
    int count=10;
    int num=0;
    while(n>0){
        num+=(n-zero(len)+1)*len;
        n=zero(len)-1;
        len--;
    }
    printf("%d",num);
}