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  • cf 1017C

    C. The Phone Number
    time limit per test
    1 second
    memory limit per test
    256 megabytes
    input
    standard input
    output
    standard output

    Mrs. Smith is trying to contact her husband, John Smith, but she forgot the secret phone number!

    The only thing Mrs. Smith remembered was that any permutation of nn can be a secret phone number. Only those permutations that minimize secret value might be the phone of her husband.

    The sequence of nn integers is called a permutation if it contains all integers from 11 to nn exactly once.

    The secret value of a phone number is defined as the sum of the length of the longest increasing subsequence (LIS) and length of the longest decreasing subsequence (LDS).

    A subsequence ai1,ai2,,aikai1,ai2,…,aik where 1i1<i2<<ikn1≤i1<i2<…<ik≤n is called increasing if ai1<ai2<ai3<<aikai1<ai2<ai3<…<aik. If ai1>ai2>ai3>>aikai1>ai2>ai3>…>aik, a subsequence is called decreasing. An increasing/decreasing subsequence is called longest if it has maximum length among all increasing/decreasing subsequences.

    For example, if there is a permutation [6,4,1,7,2,3,5][6,4,1,7,2,3,5], LIS of this permutation will be [1,2,3,5][1,2,3,5], so the length of LIS is equal to 44. LDS can be [6,4,1][6,4,1], [6,4,2][6,4,2], or [6,4,3][6,4,3], so the length of LDS is 33.

    Note, the lengths of LIS and LDS can be different.

    So please help Mrs. Smith to find a permutation that gives a minimum sum of lengths of LIS and LDS.

    Input

    The only line contains one integer nn (1n1051≤n≤105) — the length of permutation that you need to build.

    Output

    Print a permutation that gives a minimum sum of lengths of LIS and LDS.

    If there are multiple answers, print any.

    Examples
    input
    Copy
    4
    output
    Copy
    3 4 1 2
    input
    Copy
    2
    output
    Copy
    2 1
    Note

    In the first sample, you can build a permutation [3,4,1,2][3,4,1,2]. LIS is [3,4][3,4] (or [1,2][1,2]), so the length of LIS is equal to 22. LDS can be ony of [3,1][3,1], [4,2][4,2], [3,2][3,2], or [4,1][4,1]. The length of LDS is also equal to 22. The sum is equal to 44. Note that [3,4,1,2][3,4,1,2] is not the only permutation that is valid.

    In the second sample, you can build a permutation [2,1][2,1]. LIS is [1][1] (or [2][2]), so the length of LIS is equal to 11. LDS is [2,1][2,1], so the length of LDS is equal to 22. The sum is equal to 33. Note that permutation [1,2][1,2] is also valid.

    #include <iostream>
    #include <cstdio>
    #include <algorithm>
    #include <cstdlib>
    #include <cstring>
    #include <cmath>
    using namespace std;
    #define  N 100009
    #define ll long long 
    #define  mem(a,b)  memset(a,b,sizeof(a))
    int n,a[N];
    /*
    分成x组,每一组y个,x*y==n,求x+y的最小值,很明显x==sqrt(n)时成立
    当n%sqrt(n)==0时,令m=n/sqrt(n),即x*m==n
    那么分成x组:LDS==x,每一组里的数升序,总体递减
    每一组m个: LIS==m
    每一组x个 :LDS=x
    分成y组  : LIS=m
    当n%sqrt!=0 时,就是再将剩下的放到另一组里
    */
    int  main()
    {
        scanf("%d",&n);
        int index=sqrt(n);//每一组index个
        int tmp=1,t;
        for(int  i=n-index;i>=0;i-=index){
            t=i;
            for(int j=0;j<index;j++){
                a[i+j]=tmp++;
            }
        }
        for(int i=0;i<t;i++)  a[i]=tmp++;//剩下的再放到另一个组里
        for(int i=0;i<n;i++){
            printf("%d%c",a[i],i==n-1?'
    ':' ');
        }
        return 0;
    }
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  • 原文地址:https://www.cnblogs.com/tingtin/p/9457984.html
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