[IOI 1998] Polygon

[题目链接]

http://poj.org/problem?id=1179

[算法]

区间DP

[代码]

#include <algorithm>
#include <bitset>
#include <cctype>
#include <cerrno>
#include <clocale>
#include <cmath>
#include <complex>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <ctime>
#include <deque>
#include <exception>
#include <fstream>
#include <functional>
#include <limits>
#include <list>
#include <map>
#include <iomanip>
#include <ios>
#include <iosfwd>
#include <iostream>
#include <istream>
#include <ostream>
#include <queue>
#include <set>
#include <sstream>
#include <stdexcept>
#include <streambuf>
#include <string>
#include <utility>
#include <vector>
#include <cwchar>
#include <cwctype>
#include <stack>
#include <limits.h>
using namespace std;
#define MAXN 55
const long long INF = 1e15;
 
int i,j,k,l,r,n;
long long num[MAXN<<];
long long mn[MAXN<<][MAXN<<],mx[MAXN<<][MAXN<<];
long long ans;
char op;
char opt[MAXN<<];
 
int main()
{
    scanf("%d",&n);
    getchar();
    for (i = ; i <= n; i++)
    {
        if (i > ) scanf(" %c",&op);
        else scanf("%c",&op);
        scanf("%lld",&num[i]);
        opt[i] = opt[i + n] = (op == 't');
        num[i+n] = num[i];
    }
    for (i = ; i <=  * n; i++)
    {
        for (j = i + ; j <=  * n; j++)
        {
            mx[i][j] = -INF;
            mn[i][j] = INF;
        }
    }
    for (i = ; i <=  * n; i++) mx[i][i] = mn[i][i] = num[i];
    for (i = ; i <= n; i++)
    {
        for (l = ; l <=  * n - i + ; l++)
        {
            r = l + i - ;
            for (k = l; k < r; k++)
            {
                if (opt[k+])
                {
                    mn[l][r] = min(mn[l][r],mn[l][k] + mn[k+][r]);
                    mx[l][r] = max(mx[l][r],mx[l][k] + mx[k+][r]);
                } else
                {
                    mn[l][r] = min(mn[l][r],min(mx[l][k] * mx[k+][r],(mx[l][k] * mn[k+][r],mn[l][k] * mx[k+][r])));
                    mx[l][r] = max(mx[l][r],max(mx[l][k] * mx[k+][r],mn[l][k] * mn[k+][r]));
                }
            }
        }
    }
    for (i = ; i <= n; i++) ans = max(ans,mx[i][i+n-]);
    printf("%lld\n",ans);
    for (i = ; i <= n; i++)
    {
        if (mx[i][i+n-] == ans)
            printf("%d ",i);
    }
    printf("\n");
 
    return ;
}