A1140. Look-and-say Sequence

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<iostream>
#include<cstdio>
#include<string>
using namespace std;
int hashTB[1000] = {0};
int main(){
    string ss = "";
    int D, N;
    cin >> D >> N;
    ss = ss + (char)('0' + D);
    for(int i = 0; i < N - 1; i++){
        char pre = ss[0];
        int cnt = 1;
        string ss2 = "";
        for(int j = 1; j < ss.length(); j++){
            if(ss[j] == pre){
                cnt++;
            }else{
                ss2 += pre;
                ss2 += (char)(cnt + '0');
                pre = ss[j];
                cnt = 1;
            }
        }
        ss2 += pre;
        ss2 += (char)(cnt + '0');
        ss = ss2;
    }
    cout << ss;
    cin >> N;
    return 0;
}

总结：

1、题意：题意不好理解时可以根据标题来猜意思。这题的意思让你看并且读出一个序列， 如一个序列是18882111，则可以读为1个1，3个8，1个2，3个1，再将其写成位在前个数描述在后的序列：11，83，21，13。再对这个新序列进行描述。