BZOJ3864 & HDU4899：Hero meet devil——题解

https://www.lydsy.com/JudgeOnline/problem.php?id=3864

http://acm.hdu.edu.cn/showproblem.php?pid=4899

给你字符集为{A,T,G,C}的字符串，问有多少长度为m的字符串，满足其最长公共子序列长度为0,1……|S|。

太神啦，看巨佬博客吧：https://www.cnblogs.com/RabbitHu/p/BZOJ3864.html

#include<cmath>
#include<queue>
#include<vector>
#include<cstdio>
#include<cctype>
#include<cstring>
#include<iostream>
#include<algorithm>
using namespace std;
typedef long long ll;
const int p=1e9+7;
const int N=15;
const int M=1010;
inline int read(){
    int X=0,w=0;char ch=0;
    while(!isdigit(ch)){w|=ch=='-';ch=getchar();}
    while(isdigit(ch))X=(X<<3)+(X<<1)+(ch^48),ch=getchar();
    return w?-X:X;
}
int s[N+4];
int m,n,ans[N+4],f[2][1<<N],last[1<<N],trans[1<<N][4];
inline int readstring(){
    int cnt=0;char ch=0;
    while(ch<'A'||ch>'Z')ch=getchar();
    while(ch>='A'&&ch<='Z'){
    if(ch=='A')s[++cnt]=0;if(ch=='T')s[++cnt]=1;
    if(ch=='G')s[++cnt]=2;if(ch=='C')s[++cnt]=3;
    ch=getchar();
    }
    return cnt;
}
void init(){
    static int d[N+4],g[N+4];
    for(int i=0;i< 1<<n;i++){
    if(i)last[i]=last[i^(i&-i)]+1;
    for(int j=0;j<n;j++)d[j+1]=d[j]+(bool)(i&(1<<j));
    for(int k=0;k<4;k++){
        for(int j=1;j<=n;j++){
        g[j]=max(g[j-1],d[j]);
        if(s[j]==k)g[j]=max(g[j],d[j-1]+1);
        }
        trans[i][k]=0;
        for(int j=0;j<n;j++)
        if(g[j+1]-g[j])trans[i][k]|=1<<j;
    }
    }
    memset(ans,0,sizeof(ans));
    memset(f,0,sizeof(f));
}
int main(){
    int T=read();
    while(T--){
    n=readstring();m=read();
    init();
    f[0][0]=1;int now=1;
    for(int i=1;i<=m;i++){
        memset(f[now],0,sizeof(f[now]));
        for(int j=0;j< 1<<n;j++){
        for(int k=0;k<4;k++){
            (f[now][trans[j][k]]+=f[now^1][j])%=p;
        }
        }
        now^=1;
    }
    for(int i=0;i< 1<<n;i++)
        (ans[last[i]]+=f[now^1][i])%=p;
    for(int i=0;i<=n;i++)printf("%d
",ans[i]);
    }
    return 0;
}