课堂练习：给定一个十进制的正整数，写下从1开始，到N的所有整数，然后数一下其中出现“1”的个数。

# include <iostream>
using namespace std;
# include <math.h>
 
int Count1Num(int Digit)
{
    int figure = 1;               //标记计数1的位数
    int curOfDigit = 0;        //当前位数字
    int lowerOfDigit = 0;    //较低位数字
    int higherOfDigit =  0;  //较高位数字
    int count = 0;
    
    while(Digit / figure != 0)
    {
                                            //取数字
        curOfDigit = (Digit / figure) % 10;
        lowerOfDigit = Digit - (Digit / figure * figure);
        higherOfDigit = Digit / (figure * 10);
        
        if(Digit <= 0)
            return 0;
        
        if(0 == curOfDigit)                    //当前数字为0时计数
        {
            count += higherOfDigit * figure;
        }
        else if(1 == curOfDigit)              //当前数字为1时计数
        {
            count += higherOfDigit * figure + lowerOfDigit + 1;
        }
        else
        {
            count += (higherOfDigit+1) * figure;
        }
        figure = figure * 10;                //数字左移一位
    }
    return count;
}

void main()
{
    int Digit;
    int max=0;
    
    while((cout<<"    需要结束测试请输入0\n请输入要测试的数值(tip:输入自然数):"<<endl)&&(cin>>Digit))
    {
        if(Digit == 0)
            break;
        
        cout<<"从数字1到数字"<<Digit<<"包含1个数为:"<<Count1Num(Digit)<<endl;
    }
}