hdu 3681 Prison Break（dp || dfs）
15Y。。。不过离当时的 hdu4766 21Y还有一段距离。。。
刚开始拿到这题就直接bfs搞 TLE了一发。。。然后发现图中那些空地是可有可无的，于是可以把图中所有F G Y抽象出来建图，然后bfs。这个思路基本正解了吧？
于是就wa了一整晚。。。拉着lyj yy了一晚上，总觉得bfs是可以转移所有状态的。。。但是就是wa到死。。。
然后就发现了网上的人都是用dp来完成状态转移的。。为什么bfs不能。。。（事实证明是我的bfs写挫了。。。）搞了个dp解法，然后就AC了。。。
即使就这么AC了，还是很不爽，心里还在怨念bfs。。。如果bfs搞不出来，那dfs呢。。。于是又搞了个dfs。。。。62ms。。无语了。。。
博客第100题来的如此艰难。。。撸完这题，apm++。。。
//用dp判断二分答案是否合法 390ms
#include<algorithm>
#include<iostream>
#include<cstring>
#include<fstream>
#include<sstream>
#include<cstdlib>
#include<vector>
#include<string>
#include<cstdio>
#include<bitset>
#include<queue>
#include<stack>
#include<cmath>
#include<map>
#include<set>
#define FF(i, a, b) for(int i=a; i<b; i++)
#define FD(i, a, b) for(int i=a; i>=b; i--)
#define REP(i, n) for(int i=0; i<n; i++)
#define CLR(a, b) memset(a, b, sizeof(a))
#define debug puts("**debug**")
#define LL long long
#define PB push_back
#define MP make_pair
using namespace std;
const int maxn = 20;
char g[maxn][maxn];
int n, m, S, tot, all, gank, goal, id[maxn], dist[maxn][maxn];
bool vis[maxn][maxn];
map<int, int> mp, mp1;
map<int, char> mp2;
struct Node
{
int u, steps;
Node(){}
Node(int a, int b) :u(a), steps(b){}
};
int dx[4] = {0, 0, 1, -1};
int dy[4] = {1, -1, 0, 0};
void bfs(int u)
{
queue<Node> q; q.push(Node(u, 0));
int xx = u/100, yy = u%100;
CLR(vis, 0); vis[xx][yy] = 1;
while(!q.empty())
{
Node T = q.front(); q.pop();
REP(i, 4)
{
int tx = T.u/100 + dx[i], ty = T.u%100 + dy[i];
if(tx<0 || tx>=n || ty<0 || ty>=m) continue;
if(vis[tx][ty] || g[tx][ty] == 'D') continue;
vis[tx][ty] = 1;
q.push(Node(tx*100+ty, T.steps+1));
if(g[tx][ty] != 'S')
{
int v = mp1[tx*100+ty];
dist[mp1[u]][v] = dist[v][mp1[u]] = T.steps+1;
}
}
}
return ;
}
void init()
{
tot = goal = 0;
CLR(dist, -1);
mp.clear(); mp1.clear(); mp2.clear();
}
void build()
{
REP(i, n)
{
scanf("%s", g[i]);
REP(j, m)
{
if(g[i][j] == 'F') id[tot] = 1, S = tot, mp2[tot] = g[i][j], mp[tot] = i*100+j, mp1[i*100+j] = tot++;
else if(g[i][j] == 'G') mp2[tot] = g[i][j], id[tot] = 2, mp[tot] = i*100+j, mp1[i*100+j] = tot++;
else if(g[i][j] == 'Y') goal |= 1<<tot, mp2[tot] = g[i][j], id[tot] = 3, mp[tot] = i*100+j, mp1[i*100+j] = tot++;
}
}
all = (1<<tot);
REP(i, tot) bfs(mp[i]);
}
int dp[15][1<<15];
bool ok(int mid)
{
CLR(dp, -1);
dp[S][1<<S] = mid;
REP(s, all) REP(u, tot) if(dp[u][s] != -1 && (s & (1<<u)))
{
if((s & goal) == goal) return true;
REP(v, tot) if(dist[u][v] > 0)
{
if(s & (1<<v)) continue;
if(dp[u][s] < dist[u][v]) continue;
int sta = s | (1<<v);
if(dp[v][sta] == -1 || dp[v][sta] < dp[u][s] - dist[u][v])
dp[v][sta] = dp[u][s] - dist[u][v];
if(mp2[v] == 'G') dp[v][sta] = mid;
}
}
return false;
}
void solve()
{
REP(i, tot) if(i != S)
{
if(mp2[i] == 'Y' && dist[S][i] < 0)
{
puts("-1");
return ;
}
}
int L = 0, R = 2*n*m, M, ans = -1;
while(L <= R)
{
M = (L + R) >> 1;
if(ok(M)) ans = M, R = M - 1;
else L = M + 1;
}
printf("%d\n", ans);
}
int main()
{
//freopen("input.txt", "r", stdin);
//freopen("output.txt", "r", stdout);
while(scanf("%d%d", &n, &m), n+m)
{
init();
build();
solve();
}
return 0;
}
//dfs爆搞 62ms。。。。
#include<algorithm>
#include<iostream>
#include<cstring>
#include<fstream>
#include<sstream>
#include<cstdlib>
#include<vector>
#include<string>
#include<cstdio>
#include<bitset>
#include<queue>
#include<stack>
#include<cmath>
#include<map>
#include<set>
#define FF(i, a, b) for(int i=a; i<b; i++)
#define FD(i, a, b) for(int i=a; i>=b; i--)
#define REP(i, n) for(int i=0; i<n; i++)
#define CLR(a, b) memset(a, b, sizeof(a))
#define debug puts("**debug**")
#define LL long long
#define PB push_back
#define MP make_pair
using namespace std;
const int maxn = 20;
char g[maxn][maxn];
int n, m, S, tot, all, gank, goal, id[maxn], dist[maxn][maxn];
bool vis[maxn][maxn];
map<int, int> mp, mp1;
map<int, char> mp2;
struct Node
{
int u, steps;
Node(){}
Node(int a, int b) :u(a), steps(b){}
};
int dx[4] = {0, 0, 1, -1};
int dy[4] = {1, -1, 0, 0};
void bfs(int u)
{
queue<Node> q; q.push(Node(u, 0));
int xx = u/100, yy = u%100;
CLR(vis, 0); vis[xx][yy] = 1;
while(!q.empty())
{
Node T = q.front(); q.pop();
REP(i, 4)
{
int tx = T.u/100 + dx[i], ty = T.u%100 + dy[i];
if(tx<0 || tx>=n || ty<0 || ty>=m) continue;
if(vis[tx][ty] || g[tx][ty] == 'D') continue;
vis[tx][ty] = 1;
q.push(Node(tx*100+ty, T.steps+1));
if(g[tx][ty] != 'S')
{
int v = mp1[tx*100+ty];
dist[mp1[u]][v] = dist[v][mp1[u]] = T.steps+1;
}
}
}
return ;
}
void init()
{
tot = goal = 0;
CLR(dist, -1);
mp.clear(); mp1.clear(); mp2.clear();
}
void build()
{
REP(i, n)
{
scanf("%s", g[i]);
REP(j, m)
{
if(g[i][j] == 'F') id[tot] = 1, S = tot, mp2[tot] = g[i][j], mp[tot] = i*100+j, mp1[i*100+j] = tot++;
else if(g[i][j] == 'G') mp2[tot] = g[i][j], id[tot] = 2, mp[tot] = i*100+j, mp1[i*100+j] = tot++;
else if(g[i][j] == 'Y') goal |= 1<<tot, mp2[tot] = g[i][j], id[tot] = 3, mp[tot] = i*100+j, mp1[i*100+j] = tot++;
}
}
all = (1<<tot);
REP(i, tot) bfs(mp[i]);
}
bool see[20];
bool dfs(int u, int res, int sta, int mid)
{
if((sta&goal) == goal) return true;
REP(v, tot) if(dist[u][v] > 0)
{
if(see[v] || res < dist[u][v]) continue;
if(mp2[v] == 'G')
{
see[v] = 1;
if(dfs(v, mid, sta|(1<<v), mid)) return true;
see[v] = 0;
}
else
{
see[v] = 1;
if(dfs(v, res-dist[u][v], sta|(1<<v), mid)) return true;
see[v] = 0;
}
}
return false;
}
bool ok(int mid)
{
CLR(see, 0);
see[S] = 1;
return dfs(S, mid, 1<<S, mid);
}
void solve()
{
REP(i, tot) if(i != S)
{
if(mp2[i] == 'Y' && dist[S][i] < 0)
{
puts("-1");
return ;
}
}
int L = 0, R = 2*n*m, M, ans = -1;
while(L <= R)
{
M = (L + R) >> 1;
if(ok(M)) ans = M, R = M - 1;
else L = M + 1;
}
printf("%d\n", ans);
}
int main()
{
//freopen("input.txt", "r", stdin);
//freopen("output.txt", "r", stdout);
while(scanf("%d%d", &n, &m), n+m)
{
init();
build();
solve();
}
return 0;
}