POJ 1179 Polygon（区间DP）

题意：把一个多边形去掉一边，再把任意相邻打两个点合并成一个点，求最大值，

注意：两个最小的数相乘可以得到最大的数。。。

#include <iostream>#include <cstdio>#include <cstring>#include <algorithm>#include <queue>#include <cmath>#include <stack>#include <map>using namespace std;#define LL long longconst LL INF =0x3f3f3f3f3f3f3f3f;int re[59];int in[59];int op[59];int inop[59];int n;LL dp[59][59];LL dp1[59][59];LL ss(int k,LL a,LL b){    if(k==1) return a+b;    else return a*b;}int oor(){    for(int i=0;i<n;i++) for(int j=0;j<n;j++) dp[i][j] = -INF,dp1[i][j] = INF;    for(int i=0;i<n;i++) dp[i][i] = re[i],dp1[i][i] = re[i];   // for(int i=n-1;i>=0;i--) cout<<re[i]<< ' ';cout<<endl;    for(int l=1;l<n;l++)    {        for(int i=n-l-1;i>=0;i--)        {            LL tmp = -INF;            LL tmp1 = INF;            for(int j=0;j<l;j++)            {                tmp = max(tmp,ss(op[i+j],dp[i][i+j],dp[i+j+1][i+l]));                tmp = max(tmp,ss(op[i+j],dp1[i][i+j],dp[i+j+1][i+l]));                tmp = max(tmp,ss(op[i+j],dp[i][i+j],dp1[i+j+1][i+l]));                tmp = max(tmp,ss(op[i+j],dp1[i][i+j],dp1[i+j+1][i+l]));                tmp1 = min(tmp1,ss(op[i+j],dp[i][i+j],dp[i+j+1][i+l]));                tmp1 = min(tmp1,ss(op[i+j],dp1[i][i+j],dp[i+j+1][i+l]));                tmp1 = min(tmp1,ss(op[i+j],dp[i][i+j],dp1[i+j+1][i+l]));                tmp1 = min(tmp1,ss(op[i+j],dp1[i][i+j],dp1[i+j+1][i+l]));            }            dp[i][i+l] = tmp;            dp1[i][i+l] = tmp1;            //cout<<tmp<<' ';        }//cout<<endl;    }    return dp[0][n-1];}int anscnt[59];void solve(){    int cnt = 0;    LL ans = -INF;    for(int i=0;i<n;i++)    {        for(int j=0;j<n;j++)        {            re[j] = in[(i+j)%n];            op[j] = inop[(i+j)%n];        }        LL k = oor();        if(ans<k)        {            cnt = 0;            anscnt[cnt++] = i;            ans = k;        }else if(ans==k)        {            anscnt[cnt++] = i;        }    }    cout<<ans<<endl;    for(int i=0;i<cnt;i++)    {        if(i) printf(" ");        printf("%d",anscnt[i]+1);    }printf("\n");}int main(){    #ifndef ONLINE_JUDGE    freopen("in.txt","r",stdin);    #endif    while(~scanf("%d",&n))    {        char ch[9];        for(int i=0;i<n;i++)        {            scanf("%s%d",ch,&in[i]);            if(ch[0]=='t') inop[i] = 1;            else inop[i] = 2;        }        int tmp = inop[0];        for(int i=0;i<n;i++) inop[i] = inop[i+1];inop[n-1] = tmp;        solve();    }    return 0;}