Open a three-dimensional marker array to mark whether Ignatius has reached the position with the key.
Since the number of keys is up to 10, you can use state compression to do
Use 1 and 0 to indicate that there is no key I, so that this person can get the key state to be used in binary number representation
Find the minimum value with BFS
#include <iostream>
#include <cstdio>
#include <cstring>
#include <queue>
using namespace Std;
const int MAXN = 30;
const int inf = 0X7FFFFFFF;
int vis[maxn][maxn][1<<10];
Char MAP[MAXN][MAXN];
int ans = ans;
struct node
{
int x, y;
int step;
int state;
};
int st_x, st_y;
int n, m;
int dx[4] = { -1,0,1,0};
int dy[4] = {0,1,0,-1};
Queue<struct node> que;
void BFs ()
{
while (Que.size ())
Que.pop ();
memset (Vis, 0, sizeof (VIS));
struct node first = {st_x, st_y, 0, 0};
Vis[st_x][st_y][0] = 1;
Que.push (first);
while (Que.size ())
{
struct node now = Que.front ();
Que.pop ();
if (map[now.x][now.y] = = ' ^ ')
{
ans = now.step;
Break
}
for (int i = 0;i < 4;i++)
{
struct node next;
Next.x = now.x + dx[i];
Next.y = Now.y + dy[i];
if (map[next.x][next.y] = = ' * ' | | next.x < 1 | | next.x > N | | Next.y < 1 | | Next.y > M)
Continue;
if (Map[next.x][next.y] >= ' A ' && map[next.x][next.y] <= ' J ')
if (! ( Now.state & (1<< (Map[next.x][next.y]-' A ')))
Continue;
if (Map[next.x][next.y] >= ' A ' && Map[next.x][next.y] <= ' J ')
{
Next.state = Now.state | (1<< (map[next.x][next.y]-' a '));
Next.step = Now.step + 1;
if (Vis[next.x][next.y][next.state])
Continue;
Que.push (next);
Vis[next.x][next.y][next.state] = 1;
Continue
}
Next.state = now.state;
Next.step = Now.step + 1;
if (Vis[next.x][next.y][next.state])
Continue;
Vis[next.x][next.y][next.state] = 1;
Que.push (next);
}
}
}
int main ()
{
Freopen ("In.txt", "R", stdin);
int time;
while (scanf ("%d%d%d", &n, &m, &time)! = EOF)
{
for (int i = 1;i <= n;i++)
{
scanf ("%s", &map[i][1]);
for (int j = 1;j <= m;j++)
if (map[i][j] = = ' @ ')
st_x = I,st_y = j;
}
ans = inf; may not reach the end, so it is possible BFS did not update ans
BFS (); So ans always initialize it.
if (ans < time)
printf ("%d\n", ans);
Else
printf (" -1\n");
}
return 0;
}
HDU 1429 bfs+ State compression
