HDU寻找最大值 递推求连续区间

通过枚举每个点作为最小值，再通过动态规划求出以每个点作为最小值的左右区间。

代码如下：

#include <cstring>
#include <cstdio>
#include <cstdlib>
#include <algorithm>
#define MAXN 100005
using namespace std;

typedef long long int Int64;

Int64 seq[MAXN], sum[MAXN], ret;

int L[MAXN], R[MAXN], N;

int main()
{
    while (scanf("%d", &N) == 1) {
        ret = -(1LL << 60);
        for (int i = 1; i <= N; ++i) {
            scanf("%I64d", &seq[i]);    
            sum[i] = sum[i-1] + seq[i];
        }
        for (int i = 1; i <= N; ++i) {
            int len = 0, j = i - 1; 
            while (j >= 1) {
                if (seq[j] < seq[i]) break;
                len += L[j] + 1;
                j = i - len - 1;
            }
            L[i] = len;
        }
        for (int i = N; i >= 1; --i) {
            int len = 0, j = i + 1;
            while (j <= N) {
                if (seq[j] < seq[i]) break;
                len += R[j] + 1;
                j = i + len + 1;
            }    
            R[i] = len;
        }
        for (int i = 1; i <= N; ++i) {
            ret = max(ret, (sum[i+R[i]]-sum[i-L[i]-1]) * seq[i]);
        }
        printf("%I64d\n", ret);
    }
    return 0;    
}