while循环遍历
#include<iostream>
#include<string>
using namespace std;
int main()
{
string s1;
string s2;
cin>>s1>>s2;
int i=0,j=0;
int res=0;
while(i<s1.size()&&j<s2.size())
{
if(s1[i]==s2[j])
{
i++;
j++;
res++;
}
else{
i++;
}
}
cout<<res;
return 0;
}