1-n的正整数中1出现的次数

//============================================================================
// Name : 100题之30.cpp
// Author :
// Version :
// Copyright : Your copyright notice
// Description : Hello World in C++, Ansi-style
//============================================================================

#include <iostream>
using namespace std;
int n1;
int f[100];

int ComputeNumber1(int n)
{
int factor=1;
int curr=0;
int first=0;
int last=0;
int num=0;
while(n/factor!=0)
{
curr=(n/factor)%10;
last=n-(n/factor)*factor;
first=n/(factor*10);
switch(curr)
{
case 0:
num+=first*factor;
break;
case 1:
num+=first*factor+last+1;
break;
default:
num+=(first+1)*factor;
break;
}
factor*=10;
}
return num;

}
int FindNumber1(int i)
{
int num=0;
while(i)
{
if(i%10==1)
num++;
i/=10;
}
return num;
}

int compute_f(int n)
{
for(int i=1;i<=n;i++)
{
f[i]=f[i-1]+FindNumber1(i);
}
return f[n];
}
int main() {
int n=12;
cout<<ComputeNumber1(n)<<endl;
return 0;
}