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| 1 | +#include<iostream> |
| 2 | +#include<cmath> |
| 3 | +using namespace std; |
| 4 | +int balancedBTs_3(int n){ |
| 5 | + int *ans=new int[n+1]; |
| 6 | + int mod=(int)pow(10,9)+7; |
| 7 | + ans[0]=1; |
| 8 | + ans[1]=1; |
| 9 | + for(int i=2;i<=n;i++){ |
| 10 | + ans[i]=(ans[i-1]*((2*ans[i-2])%mod+ans[i-1])%mod)%mod; |
| 11 | + } |
| 12 | + return ans[n]; |
| 13 | +} |
| 14 | +int balancedBTs_helper(int h,int*ans){ |
| 15 | + if(h<=1){ |
| 16 | + return 1; |
| 17 | + } |
| 18 | + if(ans[h]!=-1){ |
| 19 | + return ans[h]; |
| 20 | + } |
| 21 | + int mod=(int) (pow(10,9))+7; |
| 22 | + int x=balancedBTs_helper(h-1,ans); |
| 23 | + int y=balancedBTs_helper(h-2,ans); |
| 24 | + int temp1=(int)(((long)(x)*x)%mod); |
| 25 | + int temp2=(int)((2*(long)(x)*y)%mod); |
| 26 | + int output=(temp1+temp2)%mod; |
| 27 | + ans[h]=output; |
| 28 | + return ans[h]; |
| 29 | + |
| 30 | +} |
| 31 | +int balancedBTs_2(int h){ |
| 32 | + int *ans=new int[h+1]; |
| 33 | + for(int i=0;i<=h;i++){ |
| 34 | + ans[i]=-1; |
| 35 | + } |
| 36 | + return balancedBTs_helper(h,ans); |
| 37 | +} |
| 38 | +int balancedBTs(int h){ |
| 39 | + if(h<=1){ |
| 40 | + return 1; |
| 41 | + } |
| 42 | + int mod=(int) (pow(10,9))+7; |
| 43 | + int x=balancedBTs(h-1); |
| 44 | + int y=balancedBTs(h-2); |
| 45 | + int temp1=(int)(((long)(x)*x)%mod); |
| 46 | + int temp2=(int)((2*(long)(x)*y)%mod); |
| 47 | + int ans=(temp1+temp2)%mod; |
| 48 | + //int ans=(x*x+2*x*y)%mod; |
| 49 | + return ans; |
| 50 | +} |
| 51 | +int main(){ |
| 52 | + int h; |
| 53 | + cin>>h; |
| 54 | + cout<<balancedBTs_3(h)<<endl; |
| 55 | + |
| 56 | + |
| 57 | + return 0; |
| 58 | +} |
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