Luogu1880 [NOI1995]石子合并 （区间DP）

一个1A主席树的男人，沦落到褪水DP举步维艰

#include <iostream>
#include <cstdio>
#include <cstring>
#include <algorithm>
#include <cmath>
#define R(a,b,c) for(register int  a = (b); a <= (c); ++ a)
#define nR(a,b,c) for(register int  a = (b); a >= (c); -- a)
#define Max(a,b) ((a) > (b) ? (a) : (b))
#define Min(a,b) ((a) < (b) ? (a) : (b))
#define Fill(a,b) memset(a, b, sizeof(a))
#define Abs(a) ((a) < 0 ? -(a) : (a))
#define Swap(a,b) a^=b^=a^=b
#define ll long long

//#define ON_DEBUG

#ifdef ON_DEBUG

#define D_e_Line printf("\n\n----------\n\n")
#define D_e(x)  cout << #x << " = " << x << endl
#define Pause() system("pause")
#define FileOpen() freopen("in.txt","r",stdin);

#else

#define D_e_Line ;
#define D_e(x)  ;
#define Pause() ;
#define FileOpen() ;

#endif

struct ios{
    template<typename ATP>ios& operator >> (ATP &x){
        x = 0; int f = 1; char c;
        for(c = getchar(); c < '0' || c > '9'; c = getchar()) if(c == '-')  f = -1;
        while(c >= '0' && c <= '9') x = x * 10 + (c ^ '0'), c = getchar();
        x*= f;
        return *this;
    }
}io;
using namespace std;

const int N = 507;
int f_max[N][N], f_min[N][N], a[N], sum[N];

int main(){
	FileOpen();
	int n;
    io >> n;
    R(i,1,n){
    	io >> a[i];
    	a[i + n] = a[i];
    }
    R(i,1, n << 1) sum[i] = sum[i - 1] + a[i];

    R(len, 2, n){
        R(l, 1, n << 1){
            int r = l + len - 1;
            if(r > (n << 1)) continue;

            f_min[l][r] = 0x3f3f3f3f;

            R(k, l, r - 1){
                f_min[l][r] = Min(f_min[l][r], f_min[l][k] + f_min[k+1][r] + sum[r] - sum[l-1]);
                f_max[l][r] = Max(f_max[l][r], f_max[l][k] + f_max[k+1][r] + sum[r] - sum[l-1]);
            }
        }
    }

    int maxx = 0, minn = 0x7fffffff;
    R(i,1,n){
    	maxx = Max(maxx, f_max[i][i + n - 1]);
    	minn = Min(minn, f_min[i][i + n - 1]);
    }

    printf("%d\n%d", minn, maxx);

    return 0;
}