题目 1255: [蓝桥杯][算法提高]能量项链

#include<bits/stdc++.h>
#include<unordered_map>
#include<unordered_set>
#define MAX 1111

const int MOD = 100000;
const int INF = 0x3f3f3f3f;
const double Pi = 3.1415926;
const double gap = 0.0000001;
using namespace std;

typedef long long int ll;

typedef unsigned long long int ull;

typedef pair<int, int> Pair;

int dp[MAX][MAX];
int n;

int main(void)
{
	int len = 0;
	int l,r,k;
	int i = 0;
	int pos = 0;
	int temp = 0;
	vector<vector<int>> a = {{0,0}}; 
	cin >> n;	

	for(i=1; i<=n; ++i)
	{
		cin >> temp;

		a.push_back({temp, 0});
		a[i-1][1] = a[i][0];
	}

	a[n][1] = a[1][0];

	for(i=1; i<=n; ++i)
		a.push_back(a[i]);

	int ans = -INF;
	for(len=2; len <=n; ++len)
		for(l=1; l+len-1<=2*n; ++l)
		{
			r = l+len-1;
			for(k=l; k<r; ++k)
				dp[l][r] = max(dp[l][r], dp[l][k]+dp[k+1][r] + a[l][0]*a[k][1]*a[r][1]);
			ans = max(dp[l][r], ans);
		}

	cout << ans <<endl;
	return 0;
}