PAT-2017年冬季考试-甲级-7-1 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

AC代码：

#include <bits/stdc++.h> using namespace std; int main(){ string s; int n,j; cin>>s>>n; for(int cnt=1;cnt<n;cnt++){ string t; for(int i=0;i<s.length();i=j){ for( j=i;j<s.length() && s[j]==s[i];j++); t+=s[i]+to_string(j-i); } s=t; } cout<<s; system("pause"); return 0; }