洛谷P1941飞扬的小鸟——细节DP

Posted 2020-10-25 Zinn

题目：https://www.luogu.org/problemnew/show/P1941

此题主要注意许多细节，详见代码。

代码如下：

#include<iostream>
#include<cstdio>
#include<cstring>
using namespace std;
int n,m,k,up[10005],down[10005],p[10005],l[10005],h[10005],f[10005][1005],wall[10005];
int INF=1e7;
bool vis[10005];
int main()
{
	scanf("%d%d%d",&n,&m,&k);
	for(int i=0;i<n;i++)
		scanf("%d%d",&up[i],&down[i]);
	for(int i=1;i<=k;i++)
		scanf("%d%d%d",&p[i],&l[i],&h[i]),wall[p[i]]=i;
	memset(f,11,sizeof f);
	for(int j=1;j<=m;j++)f[0][j]=0;
	for(int i=1;i<=n;i++)
	{
		for(int j=1;j<=m;j++)
		{
//			if(wall[i]&&(j<=l[wall[i]]||j>=h[wall[i]]))continue;//不可部分！ 
			if(j==m)
				for(int k=0;k<=up[i-1]&&j-k>0;k++)//k=0
				{
					if(!wall[i-1]||(wall[i-1]&&j-k>l[wall[i-1]]&&j-k<h[wall[i-1]]))
						f[i][j]=min(f[i][j],min(f[i-1][j-k]+1,f[i][j-k]+1));
					else f[i][j]=min(f[i][j],f[i][j-k]+1);
				}
			else if(j-up[i-1]>0)
			{
				if(!wall[i-1]||(wall[i-1]&&j-up[i-1]>l[wall[i-1]]&&j-up[i-1]<h[wall[i-1]]))
					f[i][j]=min(f[i][j],min(f[i-1][j-up[i-1]]+1,f[i][j-up[i-1]]+1));
				else f[i][j]=min(f[i][j],f[i][j-up[i-1]]+1);
			}
			//不可又降又升 
			if(f[i][j]<INF&&(!wall[i]||(wall[i]&&j>l[wall[i]]&&j<h[wall[i]])))
				vis[i]=1;
		}
		for(int j=1;j<=m;j++)
			if(j+down[i-1]<=m&&
				(!wall[i-1]||(wall[i-1]&&j+down[i-1]>l[wall[i-1]]&&j+down[i-1]<h[wall[i-1]])))
				{
					f[i][j]=min(f[i][j],f[i-1][j+down[i-1]]);
					if(f[i][j]<INF&&(!wall[i]||(wall[i]&&j>l[wall[i]]&&j<h[wall[i]])))
						vis[i]=1;
				}
	}
	if(vis[n])
	{
		int mn=INF;
		for(int j=1;j<=m;j++)
			if(f[n][j]<mn)mn=f[n][j];
		printf("1\n%d",mn);
	}
	else
	{
		int nw,ans=0;
		for(int i=n;i>=1;i--)
			if(vis[i])
			{
				nw=i;
				break;
			}
		for(int i=1;i<=nw;i++)
			if(wall[i])ans++;
		printf("0\n%d",ans);
	}
	return 0;
}