按字节截取字符串

 

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#include<iostream>
#include<string>
using namespace std;
bool isnums(char a)
{
    if((a>='A'&&a<='Z')||(a>='a'&&a<='z'))
        return true;
    return false;
}
int main()
{
    string str;
    int n;
    while(cin>>str>>n)
    {
        if(isnums(str[n-1])==true||(isnums(str[n-1])==false&&isnums(str[n-2])==false))
            cout<<str.substr(0,n)<<endl;
        else if(isnums(str[n-1])==false&&isnums(str[n-2])==true)
            cout<<str.substr(0,n-1)<<endl;
    }
}