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  • B. Code For 1 分治

    time limit per test
    2 seconds
    memory limit per test
    256 megabytes
    input
    standard input
    output
    standard output

    Jon fought bravely to rescue the wildlings who were attacked by the white-walkers at Hardhome. On his arrival, Sam tells him that he wants to go to Oldtown to train at the Citadel to become a maester, so he can return and take the deceased Aemon's place as maester of Castle Black. Jon agrees to Sam's proposal and Sam sets off his journey to the Citadel. However becoming a trainee at the Citadel is not a cakewalk and hence the maesters at the Citadel gave Sam a problem to test his eligibility.

    Initially Sam has a list with a single element n. Then he has to perform certain operations on this list. In each operation Sam must remove any element x, such that x > 1, from the list and insert at the same position  sequentially. He must continue with these operations until all the elements in the list are either 0 or 1.

    Now the masters want the total number of 1s in the range l to r (1-indexed). Sam wants to become a maester but unfortunately he cannot solve this problem. Can you help Sam to pass the eligibility test?

    Input

    The first line contains three integers nlr (0 ≤ n < 250, 0 ≤ r - l ≤ 105, r ≥ 1, l ≥ 1) – initial element and the range l to r.

    It is guaranteed that r is not greater than the length of the final list.

    Output

    Output the total number of 1s in the range l to r in the final sequence.

    Examples
    input
    7 2 5
    output
    4
    input
    10 3 10
    output
    5
    Note

    Consider first example:

    这个题目做的挺漂亮嘛!哈哈!

    #include<cstdio>
    #include<algorithm>
    #include<cmath>
    #include<vector>
    #include<iostream>
    #define MAXN 200009
    #define eps 1e-11 + 1e-12/2
    typedef long long LL;
    
    using namespace std;
    /*
    显然!分治!
    */
    LL n, l ,r;
    LL solve(LL x, LL beg,LL end)
    {
        LL mid = (beg + end) / 2;
        if (beg == mid) return 1;
        if (r < mid)
            return solve(x / 2, beg, mid - 1);
        else if (l > mid)
            return solve(x / 2, mid + 1, end);
        else
        {
            LL ret = x % 2;
            if (l < mid) ret += solve(x / 2, beg, mid - 1);
            if (r > mid) ret += solve(x / 2, mid + 1, end);
            return ret;
        }
        return 0;
    }
    int main()
    {
        
            cin >> n >> l >> r;
            if (n == 0)
            {
                cout << 0 << endl;
                return 0;
            }
            LL len = pow(2, floor(log2(n)) + 1) - 1;
            cout << solve(n, 1, len) << endl;
    }
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  • 原文地址:https://www.cnblogs.com/joeylee97/p/7281844.html
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