描述
题解
本来拿着V1的改了一下,将环改成了线……然而,25组数据T了12组,当然这也是情理之中的事,毕竟数据一下子大了那么多。
这里需要用到四边形优化,十分有趣的一个东西,详细的可以看看算导,貌似有。
代码
#include <iostream>
using namespace std;
const int MAXN = 2020;
const int INF = 0x3f3f3f3f;
int A[MAXN];
int S[MAXN][MAXN];
int W[MAXN][MAXN];
int dp[MAXN][MAXN] = {
0};
int main(int argc, const char * argv[])
{
int N;
cin >> N;
for (int i = 1; i <= N; i++)
{
cin >> A[i];
A[i + N] = A[i];
}
int N_ = 2 * N;
for (int i = 1; i < N_; i++)
{
for (int j = i; j <= i + N; j++)
{
W[i][j] = W[i][j - 1] + A[j];
}
S[i][i] = i;
}
for (int len = 2; len <= N; len++)
{
for (int i = 1; i + len - 1 <= N_; i++)
{
int j = i + len - 1;
dp[i][j] = INF;
for (int k = S[i][j - 1]; k <= S[i + 1][j]; k++)
{
int temp = dp[i][k] + dp[k + 1][j] + W[i][j];
if (temp < dp[i][j])
{
dp[i][j] = temp;
S[i][j] = k;
}
}
}
}
int res = INF;
for (int i = 1; i <= N; i++)
{
res = res < dp[i][i + N - 1] ? res : dp[i][i + N - 1];
}
cout << res << endl;
return 0;
}