注意你写成for(j=i;j<s.size();j++){if( ))}他会一直循环

#include<iostream>
#include<string>

using namespace std;
int main()
{
    int n;
    cin>>n;
    while(n--)
    {
        string s;
        cin>>s;
        int max=0,j=0,i=0;
        char c;
        for(i=0;i<s.size();i++)
        {
            int count=0;
            j=i;
            while(j<s.size()&&s[i]==s[j])
            {
                j++;
                count++;
            }
            if(count>max)
            {
                max=count;
                c=s[i];
            }
            i=j-1;
        }
        cout<<c<<' '<<max<<endl;    
    }
    return 0;
}