1140 Look-and-say Sequence

Look-and-say sequence is a sequence of integers as the following:

D, D1, D111, D113, D11231, D112213111, ...

where D is in [0, 9] except 1. The (n+1)st number is a kind of description of the nth number. For example, the 2nd number means that there is one D in the 1st number, and hence it is D1; the 2nd number consists of one D (corresponding to D1) and one 1 (corresponding to 11), therefore the 3rd number is D111; or since the 4th number is D113, it consists of one D, two 1's, and one 3, so the next number must be D11231. This definition works for D = 1 as well. Now you are supposed to calculate the Nth number in a look-and-say sequence of a given digit D.

Input Specification:

Each input file contains one test case, which gives D (in [0, 9]) and a positive integer N (≤ 40), separated by a space.

Output Specification:

Print in a line the Nth number in a look-and-say sequence of D.

Sample Input:

1 8

Sample Output:

1123123111

外观数列：

#include 
#include 
using namespace std;
 
int main() {
	int n, cnt = 0;
	string s, d;
	char c;
	cin >> d >> n;
	for (int i = 2; i <= n; i++) {
		s = "";
		if (d.size() == 1) {
			s += d[0];
			s += '1';
			d = s;
			continue;
		}
		for (int j = 1; j <= d.size(); j++) {
			c = d[j - 1];
			cnt = 1;
			while (d[j] == c && j < d.size()) {
				j++;
				cnt++;
			}
			s += c;
			s += to_string(cnt);
		}
		d = s;
	}
	cout << d;
	return 0;
}