石子合并（区间DP经典例题）

题目链接：https://www.luogu.org/problemnew/show/P1880

#include <cstdio>
#include <cmath>
#include <cstring>
#include <string>
#include <cstdlib>
#include <sstream>
#include <iostream>
#include <queue>
#include <stack>
#include <set>
#include <map>
#include <algorithm>
#include <functional>
using namespace std;
#define ll long long
#define re register
#define fi first
#define se second
#define mp make_pair
#define pb push_back
#define P pair<int,int>
const int N=1e6+10;
const int mod=1e9+7;
void read(int &a)
{
    a=0;
    int d=1;
    char ch;
    while(ch=getchar(),ch>'9'||ch<'0')
        if(ch=='-')
            d=-1;
    a=ch-'0';
    while(ch=getchar(),ch>='0'&&ch<='9')
        a=a*10+ch-'0';
    a*=d;
}
void write(int x)
{
    if(x<0)
        putchar(45),x=-x;
    if(x>9)
        write(x/10);
    putchar(x%10+'0');
}
int f1[205][205],f2[205][205],s[205];
int main()
{
    int n;
    read(n);
    for(re int i=1;i<=n;i++)
    {
        read(s[i]);
        s[i+n]=s[i];
    }
    for(re int i=1;i<=2*n;i++)
        s[i]=s[i-1]+s[i];
    int j;
    for(re int k=1;k<n;k++)
    {
        for(re int i=1,j=i+k;j<2*n&&i<2*n;i++,j++)
        {
            f2[i][j]=0x3fffffff;
            for(re int t=i;t<j;t++)
                f1[i][j]=max(f1[i][j],f1[i][t]+f1[t+1][j]+s[j]-s[i-1]),f2[i][j]=min(f2[i][j],f2[i][t]+f2[t+1][j]+s[j]-s[i-1]);
        }
    }
    int ans1=0x3fffffff,ans2=0;
    for(re int i=1;i<=n;i++)
        ans1=min(ans1,f2[i][i+n-1]),ans2=max(ans2,f1[i][i+n-1]);
    write(ans1);
    putchar('
');
    write(ans2);
    putchar('
');
    return 0;
}