luogu 4401 矿工配餐 多维dp

五维dp，记忆化搜索会MLE超内存，所以用滚动数组，十分经典

五维dp

#include <bits/stdc++.h>

using namespace std;
const int maxn=;
int n,tp[maxn],now[][][][],last[][][][];
char s[maxn];
int trans(char c){
    if(c=='M')return ;
    if(c=='F')return ;
    if(c=='B')return ;
    return -;
}
int judge(int a,int b,int c){
    if(!a && !b) return ;
    if(!a )return (b!=c)+;
    if(a==b && b==c)return ;
    return (a!=b)+(b!=c)+(c!=a);
}
int main(){
    //freopen("77.in","r",stdin);
    //freopen("77.out","w",stdout);
    scanf("%d",&n);
    scanf("%s",s);
    for(int i=;i<=n;i++)
        tp[i]=trans(s[i-]);
    for(int i=n;i>=;i--){
        memset(now,,sizeof now);
        int p1,p2;
        for(int a1=;a1<=;a1++)
        for(int a2=;a2<=;a2++)
        for(int b1=;b1<=;b1++)
        for(int b2=;b2<=;b2++){
            p1=judge(a1,a2,tp[i]),p2=judge(b1,b2,tp[i]);
            now[a1][a2][b1][b2]=max(last[a2][tp[i]][b1][b2]+p1,last[a1][a2][b2][tp[i]]+p2);
        }swap(now,last);
    }
    printf("%d",last[][][][]);
    return ;
}

记忆化搜索

#include <iostream>
#include <cstdio>
using namespace std;
const int maxn=;
int n,tp[maxn],f[maxn][][][][];

int trans(char c){
    if(c=='M')return ;
    if(c=='F')return ;
    if(c=='B')return ;
    return -;
}
int judge(int a,int b,int c){
    if(!a && !b) return ;
    if(!a )return (b!=c)+;
    if(a==b && b==c)return ;
    return (a!=b)+(b!=c)+(c!=a);
}
int dp(int now,int a1,int a2,int b1,int b2){
    if(now>n) return ;
    if(f[now][a1][a2][b1][b2]) return f[now][a1][a2][b1][b2];
    f[now][a1][a2][b1][b2]=max( dp(now+,a2,tp[now],b1,b2)+judge(a1,a2,tp[now]),dp(now+,a1,a2,b2,tp[now])+judge(b1,b2,tp[now]) );
    return f[now][a1][a2][b1][b2];
}
char s[maxn];
int main(){
    freopen("77.in","r",stdin);
    freopen("77.out","w",stdout);
    scanf("%d",&n);
    scanf("%s",s);
    for(int i=;i<=n;i++){
        int t=trans(s[i-]);
        tp[i]=t;
    }printf("%d\n",dp(,,,,));
    return ;
}

用于复习了