AC

//截取字符串并返回一个字符串
static string str_shu(string s,int n) {
string result = "";
int count = 1;
string s1 = "";
for (int i = 1; i < s.size(); i++){
if (s[i] == s[i - 1]) {
count++;
}else {
s1 += count + '0'; // 将数字转换成字符
s1 += s[i - 1]; // 拼接字符串
count = 1;
}
}
s1 += count + '0';
s1 += s[s.size() - 1];
result = s1;
if (n == 1){
return result;
}
return str_shu(result,--n);
}