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<bits/stdc++.h> using namespace std; const int maxn=1010; int main(){ map<char,int> mp; int m; string s; int cnt; cin>>s>>m; for(int i=0;i<m-1;i++){//注意是m-1 mp.clear(); string ss=""; for(int j=0;j<s.length();j++){ cnt=0; ss+=s[j]; while(s[j+1]==s[j]){ cnt++; j++; } if(cnt>0){ cnt++; ss+=(cnt+'0'); } else{ ss+='1'; } } s=ss; } printf("%s\n",s.c_str()); return 0; }