H. Colorful Balls (ICPC Preli 2k18)

#include <cstdio>
#include <cstring>
#define S 100000
#define ll long long
ll pos[S+5][2], pw[S+5], M=1e9+7, ans;
void hishab(){//2nd idx0=Same, idx1=Defrent.
    pos[0][0]=pos[0][1]=1;
    pos[1][0]=2, pos[1][1]=1;
    pw[0]=1ll, pw[1]=2ll;
    for (int i=2; i<S; i++){
        pw[i]=(pw[i-1]*2ll)%M;
        pos[i][0]=(2ll*pos[i-1][1])%M;
        pos[i][1]=(pos[i-1][0]+pos[i-1][1])%M;
    }
}
int main(){
    //freopen("in.txt","r",stdin);
    hishab();
    int t,cs=1;
    char s[S+5],c;
    scanf("%d",&t);
    while (t--){
        scanf("%s",s);
        int l=strlen(s),i,f=0;
        ans=1, c='-';
        for (i=0; i<l; i++){
            if (s[i]=='W') f++;
            else{
                if (c=='-') ans=pw[f];
        else if (c==s[i]) ans=(ans*pos[f][0])%M;
                else            ans=(ans*pos[f][1])%M;
                c=s[i], f=0;
            }
        } if (f) {
            if (c=='-') ans=(3ll*pw[f-1])%M;
            else ans=(ans*pw[f])%M;
        }
        printf("Case %d: %lld\n",cs++,ans);
    } return 0;
}