整数中1出现的次数（从1到n整数中1出现的次数）

class Solution {
public:
    int NumberOf1Between1AndN_Solution(int n)
    {
        int vsum = 0;
        int nn = n;
        int Md = 1;
        while(n != 0){
            int pv = n%10;
            int prev = n/10;
            Md *= 10;
            n /= 10;
            if(pv == 0){
                vsum += (nn/Md) * Md/10;
            }else if(pv == 1){
                if(Md == 10){
                    //特判当个位为1的情况
                    vsum += (nn/Md)* Md/10 + 1;
                }else{
                    vsum += (nn/Md)* Md/10 + (nn%(Md/10)+1);
                }
            }else{
                vsum += ((nn/Md) + 1) * Md/10;
            }
        }
        return vsum;
    }
};