HDU 2571 命运

题源

这是一道简单的dp，然而我花了不少时间。。。。。
关键是这题有负数存在，所以初始化的时候要小心一点，还有关键的dp[0][1] = dp[1][0] = 0，（这么基础的地方卡了我好久）

下面是代码：

#include <iostream>
#include <algorithm>
#include <cstdio>
#include <vector>
using namespace std;
int dp[21][1001] = { {0} };
int n, m;
bool  prime[1000 + 1] = { 0 };
vector<int> v;
void init()
{
	for (int i = 0; i <= 1000; i++) dp[0][i] = -1e9;
	for (int i = 0; i <= 20; i++) dp[i][0] = -1e9;
	prime[0] = prime[1] = true;
	for (int i = 2; i <= 1000; i++)
	{
		if (!prime[i])
		{
			v.push_back(i);
			for (int j = i * 2; j <= 1000; j+=i)
			{
				prime[j] = true;
			}
		}
	}
}
int main()
{
	v.push_back(1);
	init();
	//cout << v.size() << endl;
	int t; cin >> t;
	while (t--)
	{
		cin >> n >> m;
		for (int i = 1; i <= n; i++)
		{
			for (int j = 1; j <= m; j++)
			{
				scanf("%d", &dp[i][j]);
			}
		}
		dp[1][0] = dp[0][1] = 0;
		for (int i = 1; i <= n; i++)
		{
			for (int j = 1; j <= m; j++)
			{
				int tmp = dp[i][j];
				dp[i][j] = max(dp[i - 1][j],dp[i][j-1]);
				for (int k = 0; v[k] <= j && k < v.size(); k++)
				{
					if (!(j % v[k]))
						dp[i][j] = max(dp[i][j], dp[i][j/v[k]]);
				}
				dp[i][j] += tmp;
			}
		}
		cout << dp[n][m] << endl;
	}
	return 0;
}