1140 Look-and-say Sequence (20 分)

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

 

就是套循环了，n+1是用来描述n的。

 

 1 #include <bits/stdc++.h>
 2 using namespace std;
 3 int n,m;
 4 int main(){
 5     cin >> n >> m;
 6     string s, st;
 7     s += n+'0';
 8     m--;
 9     while(m--){
10         char c = s[0];
11         int num = 1;
12         for(int i = 1; i < s.length(); i++){
13             if(c == s[i]){
14                 num++;
15             }else{
16                 st += c;
17                 st += '0'+num;
18                 c = s[i];
19                 num = 1;
20             }
21         }
22         st += c;
23         st += '0'+num;
24         s = st;
25         st = "";
26     }
27     cout << s <<endl;
28     return 0;
29 }