1140 Look-and-say Sequence （20 分）

1140看说序列算法解析

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本文探讨了看说序列（Look-and-say Sequence）的生成算法，这是一种基于描述前一个数字符号组成的整数序列。文章通过具体实例解释了序列的形成规则，并提供了一段C++代码实现，用于计算给定数字D的第N个看说序列数。

1140 Look-and-say Sequence （20 分）

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<cstdlib>
#include<cstdio>
#include<vector>
using namespace std;
int main() {
    int d,n;
    scanf("%d%d",&d,&n);
    vector<int> num;
    num.push_back(d);
    for(int i=1;i<n;i++)
    {
        vector<int> temp;
        int v=num[0];
        int cnt=0;
        for(int j=0;j<num.size();j++)
        {
            if(num[j]==v) cnt++;
            else
            {
                temp.push_back(v);
                temp.push_back(cnt);
                cnt=1;
                v=num[j];
            }
            if(j==num.size()-1)
            {
                temp.push_back(v);
                temp.push_back(cnt);
            }
        }
        num=temp;
    }
    for(int i=0;i<num.size();i++)
    {
        printf("%d",num[i]);
    }
    return 0;
}