P1220 关路灯 区间dp

#include

using namespace std;
const int maxn = 1005;  
int dp[maxn][maxn][2], x[maxn],w[maxn] ,n,c, sum[maxn];  
int main()
{
	cin >> n>>c;  
	memset(dp, 0x3f, sizeof(dp));  
	for(int i=1; i<=n; i++)
	{
		cin >>x[i]>>w[i];  
		sum[i]=sum[i-1]+w[i];  
	}
	for(int i=1; i<=n; i++)
	{
		dp[i][i][0] =dp[i][i][1]= abs(x[c]-x[i])*(sum[n]-w[c]);  
	}
	for(int len=2; len<=n; len++)
	{
		for(int i=1; i+len-1<=n; i++)
		{
			int j = i+len-1;  
			dp[i][j][0] = min(dp[i][j][0], dp[i+1][j][0]+abs(x[i]-x[i+1])*(sum[n]+sum[i]-sum[j]));
			dp[i][j][0] = min(dp[i][j][0], dp[i+1][j][1]+abs(x[i]-x[j])*(sum[n]+sum[i]-sum[j]));
			
			dp[i][j][1] = min(dp[i][j][1], dp[i][j-1][0]+abs(x[j]-x[i])*(sum[n]+sum[i-1]-sum[j-1]));
			dp[i][j][1] = min(dp[i][j][1],  dp[i][j-1][1]+abs(x[j]-x[j-1])*(sum[n]+sum[i-1]-sum[j-1])); 
		}
	} 
	cout << min(dp[1][n][0], dp[1][n][1]);  
	return 0;
}