题解（函数+判断）

#include <bits/stdc++.h>
using namespace std;

int countOnes(int n) {
vector<int> nums;
for (int i = 1; i <= n; ++i) {
nums.push_back(i);
}

int count = 0;
for (int x : nums) {
    while (x) {
        if (x % 10 == 1)
            ++count;
        x /= 10;
    }
}
return count;

}

int main() {
int n;
cin >> n;
if(n<0){
n = abs(n);
cout << countOnes(n);
}
else if(n==0){
cout<<0;
}
else{

cout << countOnes(n);
return 0;

}

}