题目描述

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

代码

#include <iostream>
#include <string>
using namespace std;
int main() {
    string d;
    int n, k;
    cin >> d >> n;
    for (int i = 1; i < n; i++) {
        string t;
        for (int j = 0; j < d.size(); j = k) {
            for (k = j; k < d.size() && d[j] == d[k]; k++);
            t += d[j] + to_string(k - j);
        }
        d = t;
    }
    cout << d;
    return 0;
}