Educational Codeforces Round 1 A. Tricky Sum 暴力
A. Tricky Sum
Time Limit: 20 Sec
Memory Limit: 256 MB
题目连接
http://codeforces.com/contest/598/problem/A
Description
In this problem you are to calculate the sum of all integers from 1 to n, but you should take all powers of two with minus in the sum.
For example, for n = 4 the sum is equal to - 1 - 2 + 3 - 4 = - 4, because 1, 2 and 4 are 20, 21 and 22 respectively.
Calculate the answer for t values of n.
Input
The first line of the input contains a single integer t (1 ≤ t ≤ 100) — the number of values of n to be processed.
Each of next t lines contains a single integer n (1 ≤ n ≤ 109).
Output
Print the requested sum for each of t integers n given in the input.
Sample Input
2
4
1000000000
Sample Output
-4
499999998352516354
HINT
题意
让你输出前n个数的和,但是如果遇到了2的次方,就是减去他
题解:
正常做法,就直接O(1)得到前n个数的和,然后再log判断前n个数的2的倍数的数是哪些就好了。
但是我为什么脑抽了去写二分。。。
代码
#include<iostream> #include<vector> #include<stdio.h> #include<algorithm> using namespace std; vector<long long>Q; vector<long long>Sum; int main() { long long sum = 1; while(sum < 1e9+1) { Q.push_back(sum); sum*=2; } long long Sum1 = 0; for(int i=0;i<Q.size();i++) { Sum1 += Q[i]; Sum.push_back(Sum1); } int t;scanf("%d",&t); while(t--) { long long n;cin>>n; long long ans = (1+n)*n/2; long long p = upper_bound(Q.begin(),Q.end(),n)-Q.begin(); p--; ans -= 2*Sum[p]; cout<<ans<<endl; } }