题解，第二条

#include<iostream>
#include<string>
using namespace std;
int main(){string a;int sum=0;cin>>a;
    for(int i=0;i<a.size();i++){if(a[i]>='0'&&a[i]<='9'){
            switch(a[i]){case '1':sum++;break;
                case '2':sum+=2;break;case '3':sum+=3;break;
                case '4':sum+=4;break;case '5':sum+=5;break;
                case '6':sum+=6;break;case '7':sum+=7;break;
                case '8':sum+=8;break;case '9':sum+=9;break;}}}cout<<sum;
}