2.4 N到1中1的数目

#include <iostream>
using namespace std;

#include <stdlib.h>
#include <sys/types.h>

int CountOf1(u_int32_t n)
{
    u_int32_t lower = 0;
    u_int32_t cur = 0;
    u_int32_t upper = 0;
    int count = 0;
    u_int32_t factor = 1;
    
    while (n / factor != 0) {
        lower = n % factor;
        upper = n / (10 * factor);
        cur = (n % (10 * factor))/ factor;
        switch(cur) {
        case 0:
            count += upper * factor;
            break;
        case 1:
            count += (upper * factor + lower + 1);
            break;
        default:
            count += (upper + 1) * factor;
        }
        
        factor *= 10;
    }
    
    return count;
}

int main()
{
    cout << CountOf1(11u) << endl;
    
    return 0;
}