rock paper scisors

#include <iostream>
#include <string>
#include <vector>
#include <cstdint>


using namespace std;

constexpr uint32_t M = 1000000007;

constexpr int RPS2int(char c){
    switch( c){
    case 'R': return 0;break;
    case 'P': return 1;break;
    case 'S': return 2;break;
    default: return -1;
    };
}

int score (char our, char thier){
    int res = (RPS2int(our)-RPS2int(thier) +3 )%3;
    return ((1+res)%3)-1;  //convert 2 into -1;
}


int main()
{
    std::string enemy_move;

    cin>>enemy_move;

    int n = enemy_move.size();

    vector<uint32_t> R(2*n+3), P(2*n+3), S(2*n+3);
    vector<uint32_t> R_new(2*n+3), P_new(2*n+3), S_new(2*n+3);


    R[ n+1 + score('R',enemy_move[0])]=1;
    P[ n+1 + score('P',enemy_move[0])]=1;
    S[ n+1 + score('S',enemy_move[0])]=1;

    for (int t=1; t<enemy_move.size(); t++){
        R_new[0]=R_new.back()=0;
        S_new[0]=S_new.back()=0;
        P_new[0]=P_new.back()=0;
        for (int i=1; i<R.size()-1; i++){
            R_new[i] = (P[i-score('R',enemy_move[t])] + S[i-score('R',enemy_move[t])])%M;
            P_new[i] = (R[i-score('P',enemy_move[t])] + S[i-score('P',enemy_move[t])])%M;
            S_new[i] = (P[i-score('S',enemy_move[t])] + R[i-score('S',enemy_move[t])])%M;
        }
        swap(R,R_new);
        swap(P,P_new);
        swap(S,S_new);
        cout<<"round "<<t<<endl;
    }

    uint64_t accu=0;
    for (int i=n+2; i<R.size();i++){
        accu = (accu + R[i]+P[i]+S[i])%M;
    }
    cout<<accu<<endl;

}