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  • Codeforces Round #256 (Div. 2) D. Multiplication Table 很有想法的一个二分

    D. Multiplication Table
    time limit per test
    1 second
    memory limit per test
    256 megabytes
    input
    standard input
    output
    standard output

    Bizon the Champion isn't just charming, he also is very smart.

    While some of us were learning the multiplication table, Bizon the Champion had fun in his own manner. Bizon the Champion painted ann × m multiplication table, where the element on the intersection of the i-th row and j-th column equals i·j (the rows and columns of the table are numbered starting from 1). Then he was asked: what number in the table is the k-th largest number? Bizon the Champion always answered correctly and immediately. Can you repeat his success?

    Consider the given multiplication table. If you write out all n·m numbers from the table in the non-decreasing order, then the k-th number you write out is called the k-th largest number.

    Input

    The single line contains integers nm and k (1 ≤ n, m ≤ 5·105; 1 ≤ k ≤ n·m).

    Output

    Print the k-th largest number in a n × m multiplication table.

    Examples
    input
    2 2 2
    output
    2
    input
    2 3 4
    output
    3
    input
    1 10 5
    output
    5
    题意:给你一个n*m的乘法表,得到第K大;
    思路:对于每一行的小于等于其的数,得到个数来进行判断,n(log(n*m);
    #include<bits/stdc++.h>
    using namespace std;
    #define ll __int64
    #define mod 1000000007
    #define pi (4*atan(1.0))
    const int N=1e2+10,M=1e6+10,inf=1e9+10;
    int main()
    {
        ll x,y,z,i,t;
        scanf("%I64d%I64d%I64d",&x,&y,&z);
        ll st=1;
        ll en=x*y;
        while(st<en)
        {
            ll mid=(st+en)>>1;
            ll sum=0;
            for(i=1;i<=x;i++)
            sum+=min(y,mid/i);
            if(sum>=z)
            en=mid;
            else
            st=mid+1;
        }
        cout<<st<<endl;
        return 0;
    }
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  • 原文地址:https://www.cnblogs.com/jhz033/p/5572096.html
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