Inna and Dima CodeForces - 374C
原题链接
考察:记忆化搜索
思路:
不用等完整的DIMA在记录.设置\(dp[i][j]\)为当前坐标\((i,j)\)能走的步数.求所有起点的最大\(dp[i][j]\).
无穷的条件是当前起点开始走到本次走过的地方.所以还需要一个\(bool\)数组记录.
Code
#include <iostream>
#include <cstring>
using namespace std;
const int N = 1010,INF = 0x3f3f3f3f;
int n,m,dp[N][N];//以x,y为起点能搜到的最大dima
char s[N][N],dir[N/10] = "DIMA";
bool vis[N][N];
int xx[4] = {-1,1,0,0},yy[4] = {0,0,-1,1};
int dfs(int x,int y,int idx)
{
if(dp[x][y]!=-1) return dp[x][y];
dp[x][y] = 0;
int ans = 0;
for(int i=0;i<4;i++)
{
int dx = x+xx[i],dy = y+yy[i];
if(dx>0&&dx<=n&&dy>0&&dy<=m&&s[dx][dy]==dir[idx%4])
{
if(vis[dx][dy]) return INF;
vis[dx][dy] = 1;
ans = max(dfs(dx,dy,idx+1),ans);
vis[dx][dy] = 0;
}
}
return dp[x][y] = ans+1;
}
void solve()
{
int ans = 0;
for(int i=1;i<=n;i++)
for(int j=1;j<=m;j++)
if(s[i][j]=='D'&&dp[i][j]==-1)
{
vis[i][j] = 1;
ans = max(dfs(i,j,1),ans);
vis[i][j] = 0;
}
if(ans/4==0) puts("Poor Dima!");
else if(ans>=INF) puts("Poor Inna!");
else printf("%d\n",ans/4);
}
int main()
{
scanf("%d%d",&n,&m);
memset(dp,-1,sizeof dp);
for(int i=1;i<=n;i++) scanf("%s",s[i]+1);
solve();
return 0;
}