delete pics to save space

2.10618.cpp

@@ -0,0 +1,99 @@
+#include<cstdio>
+#include<cstring>
+const int UP   =0;
+const int LEFT =1;
+const int RIGHT=2;
+const int DOWN =3;
+const int maxn =70+5;
+int d[maxn][4][4][3];
+int action[maxn][4][4][3]; 
+char str[maxn],hsh[128],fth[]=".LR";
+inline int energy(int a,int ta)
+{
+	if(a==ta) return 3;
+	if(a+ta==3) return 7;
+	return 5;
+}
+int energy(int i,int a,int b,int s,int f,int t,int& ta,int& tb)
+{
+	ta=a;tb=b;
+	if(f==1) ta=t;
+	else if(f==2) tb=t;
+	
+	if(ta==tb) return -1;//the same position
+	if(ta==RIGHT&&tb==LEFT) return -1;//turned around
+	if(a==RIGHT&&tb!=b) return -1;
+	if(b==LEFT&&ta!=a) return -1;//bad action
+	
+	int e;
+	if(f==0) e=0;
+	else if(f!=s) e=1;
+	else
+	{
+		if(f==1) e=energy(a,ta);
+		else e=energy(b,tb);
+	}
+	return e;
+}
+void update(int i,int a,int b,int s,int f,int t)
+{
+	int ta,tb;
+	int e=energy(i,a,b,s,f,t,ta,tb);
+	if(e<0) return;//bad action
+	int cost=d[i+1][ta][tb][f]+e;
+	int &res=d[i][a][b][s];
+	if(cost<res)
+	{
+		res=cost;
+		action[i][a][b][s]=f*4+t;
+	}
+}
+int main()
+{
+#ifdef local
+	freopen("pro.in","r",stdin);
+#endif
+	hsh['U'] = 0; hsh['L'] = 1; hsh['R'] = 2; hsh['D'] = 3;
+	int i,a,b,s,t;
+	while(scanf("%s",str)==1)
+	{
+		if(str[0]=='#') break;
+		int n=strlen(str);
+		memset(d,0,sizeof(d));
+		for(i=n-1;i>=0;i--)
+			for(a=0;a<4;a++)
+				for(b=0;b<4;b++)
+					if(a!=b)
+						for(s=0;s<3;s++)
+						{
+							d[i][a][b][s]=10*n;
+							if(str[i]=='.')
+							{
+								update(i,a,b,s,0,0);
+								for(t=0;t<4;t++)
+								{
+									update(i,a,b,s,LEFT ,t);
+									update(i,a,b,s,RIGHT,t);
+								}
+							}
+							else
+							{
+								update(i,a,b,s,LEFT ,hsh[str[i]]);
+								update(i,a,b,s,RIGHT,hsh[str[i]]);
+							}
+						}
+		
+		a=LEFT,b=RIGHT,s=0;
+		for(i=0;i<n;i++)
+		{
+			int f=action[i][a][b][s]/4;
+			int t=action[i][a][b][s]%4;
+			putchar(fth[f]);
+			s=f;
+			if(f==1) a=t;
+			else if(f==2) b=t;
+		}
+		printf("\n");
+	}
+	return 0;
+}