• CodeForces


    传送门:

    http://codeforces.com/problemset/problem/598/A

    A. Tricky Sum
    time limit per test
    1 second
    memory limit per test
    256 megabytes
    input
    standard input
    output
    standard output

    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.

    Examples
    Input
    Copy
    2
    4
    1000000000
    Output
    Copy
    -4
    499999998352516354
    Note

    The answer for the first sample is explained in the statement.

    分析:

    题意:

    先输入一个T,表示有几组输入,再输入一个n,表示要计算n的和sum。

    计算规则为,从1---n这n个数中任意一个数m,如果m这个数是2的次方的话,sum+=(-m),否则sum+=m。

    思路:

    先求出总的和sum,再用快速幂,求出所有是2的次方的数的和num,最后求差即可sum=sum-2*num。

    code:

    #include<bits/stdc++.h>
    using namespace std;
    typedef long long LL;
    LL qm(int n,int m)//快速幂
    {
        LL s=1,x=n;
        while(m)
        {
            if(m&1)
            {
                s*=x;
            }
            x*=x;
            m>>=1;
        }
        return s;
    }
    int main()
    {
        int t;
        cin>>t;
        LL n;
        LL sum;
        while(t--)
        {
            scanf("%I64d",&n);
            sum=n*(n+1)/2;//等差数列求和公式
            for(int i=0;qm(2,i)<=n;i++)
            {
                sum-=(2*qm(2,i));
            }
            printf("%I64d
    ",sum);
        }
        return 0;
    }
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  • 原文地址:https://www.cnblogs.com/yinbiao/p/9365127.html
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