description:
就是看前面那个数有几个几，然后写一串。
Note:
Example:
The count-and-say sequence is the sequence of integers with the first five terms as following:
1. 1
2. 11
3. 21
4. 1211
5. 111221
1 is read off as "one 1" or 11.
11 is read off as "two 1s" or 21.
21 is read off as "one 2, then one 1" or 1211.
answer:
class Solution {
public:
string countAndSay(int n) {
if (n < 0) return "";
string res = "1";
for (int i = 1; i < n; i++) {
string newres = "";
for (int k = 0; k < res.size(); ++k) {
int cnt = 1;
while(k + 1 < res.size() && res[k] == res[k +1]){
cnt += 1;
++k;
}
newres += to_string(cnt) + res[k];
}
res = newres;
}
return res;
}
};
relative point get√：
- to_string() c++中string类的内置函数