POJ 2796 Feel Good

单调栈还没有完全理解...写了个优雅的暴力AC了...

#include<cstdio>
#include<cstring>
#include<cmath>
#include<algorithm>
using namespace std;

const int maxn=100000+10;
long long a[maxn],sum[maxn];
int L[maxn],R[maxn];
int n;

int main()
{
    while(~scanf("%d",&n))
    {
        sum[0]=0;
        for(int i=1;i<=n;i++)
        {
            scanf("%lld",&a[i]);
            sum[i]=sum[i-1]+a[i];
        }

        for(int i=1;i<=n;i++) L[i]=i;
        for(int i=2;i<=n;i++)
        {
            if(a[i]>a[i-1]) continue;
            int pre=L[i-1];
            while(1)
            {
                L[i]=pre;
                if(pre==1||a[pre-1]<a[i]) break;
                pre=L[pre-1];
            }
        }

        for(int i=n;i>=1;i--) R[i]=i;
        for(int i=n-1;i>=1;i--)
        {
            if(a[i]>a[i+1]) continue;
            int pre=R[i+1];
            while(1)
            {
                R[i]=pre;
                if(pre==n||a[pre+1]<a[i]) break;
                pre=R[pre+1];
            }
        }

        long long ans1=-1;
        int ans2,ans3;
        for(int i=1;i<=n;i++){
            if(ans1<a[i]*(sum[R[i]]-sum[L[i]-1]))
            {
                ans1=a[i]*(sum[R[i]]-sum[L[i]-1]);
                ans2=L[i];
                ans3=R[i];
            }
        }
        printf("%lld
",ans1);
        printf("%d %d
",ans2,ans3);
    }
    return 0;
}