luogu P1481 魔族密码

analysis

表示不想再写DP了，用trie树干掉
建好trie树，dfs求一下树中的每一条链上最多的标记数res便是结果了

code

#include
using namespace std;
#define loop(i,start,end) for(register int i=start;i<=end;++i)
#define anri_loop(i,start,end) for(register int i=start;i>=end;--i)
#define clean(arry,num) memset(arry,num,sizeof(arry))
#define max(a,b) ((a>b)?a:b)
#define min(a,b) ((a
#define cacid(a) (a-'a')
int n,cnt=0,res=0;
const int maxn=2000+10;
int tree[75*maxn][26];
bool flag[75*maxn];
template<class T>void read(T &x)
{
    x=0;char r=getchar();T neg=1;
    while(r>'9'||r<'0'){if(r=='-')neg=-1;r=getchar();}
    while(r>='0'&&r<='9'){x=(x<<3)+(x<<1)+r-'0';r=getchar();}
    x*=neg;
}
void insert(char *s)
{
    register int len=strlen(s);
    int root=0;
    loop(i,0,len-1)
    {
        int id=cacid(s[i]);
        if(tree[root][id]==0)
        {
            tree[root][id]=++cnt;
            flag[cnt]=false;
            loop(i,0,25)tree[tree[root][id]][i]=0;
        }
        root=tree[root][id];
    }
    flag[root]=true;
}
void dfs(int pos,int cnt)
{
    res=max(res,cnt);
    loop(i,0,25)
    {
        if(tree[pos][i]!=0)dfs(tree[pos][i],cnt+((flag[tree[pos][i]])?1:0));
    }
}
int main()
{
    #ifndef ONLINE_JUDGE
    freopen("datain.txt","r",stdin);
    #endif
    read(n);
    clean(flag,false);
    clean(tree,0);
    char _s[100];
    loop(i,1,n)
    {
        scanf("%s",_s);
        insert(_s);
    }
    dfs(0,0);
    printf("%d",res);
    return 0;
}