洛谷P1220关路灯——区间DP

#include<iostream>
#include<cstdio>
using namespace std;
int n,c,pos[55],w[55],sum,s[55][55],dp[55][55][3],INF=10000006;
int main()
{
	scanf("%d%d",&n,&c);
	for(int i=1;i<=n;i++)
	{
		scanf("%d%d",&pos[i],&w[i]);
		sum+=w[i];
		if(i==c)
		{
			dp[i][i][0]=0;dp[i][i][1]=0;
		}
		else
		{
			dp[i][i][0]=INF;dp[i][i][1]=INF;
		}
	}
	for(int i=1;i<=n;i++)
	{
		int tot=0;
		for(int j=i;j<=n;j++)
		{
			tot+=w[j];
			s[i][j]=tot;
		}
	}
	for(int l=2;l<=n;l++)
		for(int i=1;i<=n-l+1;i++)
		{
			int j=i+l-1;
			dp[i][j][0]=min(dp[i+1][j][0]+(sum-s[i+1][j])*(pos[i+1]-pos[i]),
							dp[i+1][j][1]+(sum-s[i+1][j])*(pos[j]-pos[i]));
			dp[i][j][1]=min(dp[i][j-1][0]+(sum-s[i][j-1])*(pos[j]-pos[i]),
							dp[i][j-1][1]+(sum-s[i][j-1])*(pos[j]-pos[j-1]));
		}
	printf("%d",min(dp[1][n][0],dp[1][n][1]));
	return 0;
}