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  • codeforces463D

    Gargari and Permutations

     CodeForces - 463D 

    Gargari got bored to play with the bishops and now, after solving the problem about them, he is trying to do math homework. In a math book he have found k permutations. Each of them consists of numbers 1, 2, ..., n in some order. Now he should find the length of the longest common subsequence of these permutations. Can you help Gargari?

    You can read about longest common subsequence there: https://en.wikipedia.org/wiki/Longest_common_subsequence_problem

    Input

    The first line contains two integers n and k (1 ≤ n ≤ 1000; 2 ≤ k ≤ 5). Each of the next k lines contains integers 1, 2, ..., n in some order — description of the current permutation.

    Output

    Print the length of the longest common subsequence.

    Examples

    Input
    4 3
    1 4 2 3
    4 1 2 3
    1 2 4 3
    Output
    3

    Note

    The answer for the first test sample is subsequence [1, 2, 3].

    sol:求m个序列的lcs,似乎看上去很难得样子,实际上想到dp状态就不难了,dp[i]表示以数字 i 结尾的m个序列的lcs长度,然后判断一下是否所有数字 j 都在 i 之前就可以转移了

    #include <bits/stdc++.h>
    using namespace std;
    typedef int ll;
    inline ll read()
    {
        ll s=0;
        bool f=0;
        char ch=' ';
        while(!isdigit(ch))
        {
            f|=(ch=='-'); ch=getchar();
        }
        while(isdigit(ch))
        {
            s=(s<<3)+(s<<1)+(ch^48); ch=getchar();
        }
        return (f)?(-s):(s);
    }
    #define R(x) x=read()
    inline void write(ll x)
    {
        if(x<0)
        {
            putchar('-'); x=-x;
        }
        if(x<10)
        {
            putchar(x+'0'); return;
        }
        write(x/10);
        putchar((x%10)+'0');
        return;
    }
    #define W(x) write(x),putchar(' ')
    #define Wl(x) write(x),putchar('
    ')
    const int N=1005;
    int n,m,a[10][N],Pos[10][N];
    int dp[N];
    int main()
    {
        int i,j,k;
        R(n); R(m);
        for(i=1;i<=m;i++)
        {
            for(j=1;j<=n;j++)
            {
                R(a[i][j]); Pos[i][a[i][j]]=j;
            }
        }
        dp[a[1][1]]=1;
        for(i=2;i<=n;i++)
        {
            for(j=1;j<i;j++)
            {
                bool Flag=1;
                for(k=2;k<=m&&Flag;k++) if(Pos[k][a[1][j]]>Pos[k][a[1][i]]) Flag=0;
                if(Flag) dp[a[1][i]]=max(dp[a[1][i]],dp[a[1][j]]+1);
            }
            if(!dp[a[1][i]]) dp[a[1][i]]=1;
        }
        int ans=1;
        for(i=1;i<=n;i++) ans=max(ans,dp[i]);
        Wl(ans);
        return 0;
    }
    /*
    Input
    4 3
    1 4 2 3
    4 1 2 3
    1 2 4 3
    Output
    3
    */
    View Code
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  • 原文地址:https://www.cnblogs.com/gaojunonly1/p/10764300.html
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