PAT 1140 Look-and-say Sequence

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;
typedef long long ll;


int main(){
    string s;
    cin >> s;
    int n;
    cin >> n;n--;

    while(n--){
        string temp = "";
        for(int i=0;i < s.size();){
            int j = i;
            while(s[i] == s[j]&&j < s.size()){
                j++;
            }
            temp += s[i]+to_string(j-i);
            i = j;
        }
        s = temp;
    }
    cout << s;

    return 0;
}

——这题意我也是醉了，完全没说清楚，还把人误导用map，看了题解才知道啥意思。