A.Phoenix and Balance [CF1348 A] (Thinking, Water)

A.Phoenix and Balance

CF1348 A
question meaning: given $n$ operations,$i$ time you can go to$a/b$ Kagami$2^i$ , requires$both\; aandb$ are added$\frac{n}{2}$Times. Find $|a-b$ The minimum value of$|$ .
Idea:
A water problem in binary It
can be known thatfor 2ⁱ, it is greater than${\sum }_{k=1}^{i-1}{2}^i$
so suppose$b$ is a larger number, just put$2^n$ for$b$ , add the rest tobbfrom the smallest$b$ on. Give the rest to$a$。

int main(){
    
    
    int t=ird();
    LL n,a,b;
    while(t--){
    
    
        n=lrd();
        b=qpow(2,n+1)-2;
        a=qpow(2,n);
        for(int i=1;i<n/2;i++){
    
    
            a+=qpow(2,i);
        }
        b-=a;
        a-=b;
        cout<<a<<endl;
    }
}