delete pics to save space

history_source/信息学奥赛一本通/2.5.1.cpp

@@ -0,0 +1,38 @@
+#include<iostream>
+#define max(a,b) ((a)>(b)?(a):(b))
+using namespace std;
+char Map[25][25];
+int y,x,ans=-1;
+int dx[4]={0,1,0,-1},
+	dy[4]={-1,0,1,0};
+bool used[26]={0};
+bool check(int xx,int yy)
+{
+	if(xx>=0&&xx<x&&yy>=0&&yy<y&&!used[Map[xx][yy]-'A']) return 1;
+	return 0;
+}
+void dfs(int xx,int yy,int step)
+{
+	ans=max(ans,step);
+	for(int i=0;i<4;i++)
+	{
+		if(check(xx+dx[i],yy+dy[i]))
+		{
+			used[Map[xx+dx[i]][yy+dy[i]]-'A']=1;
+			dfs(xx+dx[i],yy+dy[i],step+1);
+			used[Map[xx+dx[i]][yy+dy[i]]-'A']=0;
+		}
+	}
+}
+int main()
+{
+	cin>>y>>x;
+	for(int i=0;i<y;i++)
+		for(int j=0;j<x;j++)
+			cin>>Map[j][i];
+	used[Map[0][0]-'A']=1;
+	dfs(0,0,1);
+	cout<<ans<<endl;
+	return 0;
+}
+