整数中出现1的个数

class Solution {
public:
int NumberOf1Between1AndN_Solution(int n)
{
int dev = 10; //除数
int multi = 1;
int res = 0;
int low;
int cur = n%dev; //最初为个位数
int high = n / dev; //high从十位开始
int flag = false;

    while(n / multi)  //当高位数存在时
    {
        if(cur > 1)
            res = res+ (high+1) *multi;
        if(cur == 1)
        {
            if(flag)
                res =res + high * multi + low+1;
            else
                res =1;
        }
        if(cur == 0)
        {
            res = res + high * multi;
        }
        flag = true;
        dev *= 10;
        multi *= 10;
        high = n / dev;
        cur = (n - high *dev) / multi;
        low = n - high*dev - cur *multi;
    }
    return res;
}

};