PAT A1140 Look-and-say Sequence （20 分）—

PAT A1140 Look-and-say Sequence （20 分）——数学题

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 (

Output Specification:

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

Sample Input:

1 8

Sample Output:

1123123111

 1 #include <stdio.h>
 2 #include <algorithm>
 3 #include <iostream>
 4 #include <map>
 5 #include <vector>
 6 #include <set>
 7 using namespace std;
 8 const int maxn=100100;
 9 int n,m,k;
10 int seq[50][maxn];
11 int cnt;
12 int main(){
13     scanf("%d %d",&n,&m);
14     seq[0][0]=n;
15     if(m==1)printf("%d",n);
16     cnt=1;
17     for(int i=1;i<m;i++){
18         k=0;
19         int now=seq[i-1][0],num=0;
20         for(int j=0;j<cnt;j++){
21             if(seq[i-1][j]==now){
22                 num++;
23             }
24             else{
25                 seq[i][k]=now;
26                 seq[i][k+1]=num;
27                 now=seq[i-1][j];
28                 num=1;
29                 k+=2;
30             }
31         }
32         seq[i][k]=now;
33         seq[i][k+1]=num;
34         k+=2;
35         cnt=k;
36     }
37     for(int j=0;j<k;j++){
38         printf("%d",seq[m-1][j]);
39     }
40 }

View Code

注意点：题目看了半天没懂，后来看懂了点理解的是前一个序列有几个什么然后输出，然后第六个样例怎么看都不对。看了大佬的思路，原来是有几个连续的数字，然后输出来。那既然n最大就40，设个二维数组直接枚举就好了，maxn一开始只设了10010，发现最后一个测试点错了，最后一个测试点应该是n=40，结果很大，maxn为1e5就够了

---------------- 坚持每天学习一点点