CF 959 E. Mahmoud and Ehab and the xor-MST

E. Mahmoud and Ehab and the xor-MST

https://codeforces.com/contest/959/problem/E

分析：

　　每个点x应该和x ^ lowbit(x)连边，那么现在就是求$\sum_{i=1}^{n}lowbit(i)$，然后打表找规律。

代码：

 #include<cstdio>
 #include<algorithm>
 #include<cstring>
 #include<iostream>
 #include<cmath>
 #include<cctype>
 #include<set>
 #include<queue>
 #include<vector>
 #include<map>
 using namespace std;
 typedef long long LL;

 inline int read() {
     int x=,f=;char ch=getchar();for(;!isdigit(ch);ch=getchar())if(ch=='-')f=-;
     for(;isdigit(ch);ch=getchar())x=x*+ch-'';return x*f;
 }

 int main() {
     LL n, res = ;
     cin >> n; n--;
     for (LL x = ; x <= n; x <<= )
         res += ((n - x) / (x + x) + ) * x;
     cout << res;
     return ;
 }