1140. Look-and-say Sequence (20)

1140. Look-and-say Sequence (20)
时间限制 400 ms 内存限制 65536 kB 代码长度限制 16000 B
判题程序 Standard 作者 CHEN, Yue

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

#include <iostream>
#include <string>
using namespace std;


int main()
{
#ifdef _DEBUG
    freopen("d1.txt","r+",stdin);
#endif

    string D;int N;
    string res,tmp;
    cin >> D >> N;
    tmp = D;
    while(--N){
        for(int i=0;i<tmp.size();){
            res += tmp[i]; int n = 1;
            int j =i + 1;
            for(;j< tmp.size();++j){
                if(tmp[i] == tmp[j]) ++n;
                else break;
            }
            i = j;
            res += n + '0';
        }
        tmp = res;
        res = "";
    }

    cout << tmp;
    return 0;
}