按字节截取字符串

#include <bits/stdc++.h>using namespace std;int main(){    string a;    int n;    while(cin>>a>>n)    {        int num=0;        for(int i=n-1; i>=0; i--)        {            if(a[i]>0)break;            else num++;        }        if(num%2)        {            cout<<a.substr(0,n-1)<<endl;        }        else        {            cout<<a.substr(0,n)<<endl;        }    }    return 0;}