find shorttest path

本文介绍了一种求解迷宫最短路径的算法,通过深度优先搜索的方式,从起点'S'出发,寻找到达终点'E'的最短步数。算法避免了已访问的位置和障碍物,适用于由'O'(开放)、'X'(障碍物)、'S'(起点)、'E'(终点)组成的迷宫。

 

def find_shortest_path(maze):
    '''
    maze = [['X', 'X', 'O', 'S', 'X'],
              ['X', 'X', 'O', 'O', 'X'],
              ['X', 'X', 'O', 'X', 'X'],
              ['X', 'X', 'O', 'E', 'X']]'''
    a=[]
    b=[]
    s1=s2=e1=e2=0
    for i in range(len(maze)):
        for j in range(len(maze[0])):
            if maze[i][j]=='S':
                s1=i
                s2=j
            if maze[i][j]=='E':
                e1=i
                e2=j
    a.append([(s1,s2),])
    while len(a)>0:
        b=[]
        for aaa in a:
            #up
            aa=aaa[:]
            if aa[-1][0]-1>=0:
                if aa[-1][0]-1 == e1 and aa[-1][1] == e2:
                    return len(aa)
                if maze[aa[-1][0]-1][aa[-1][1]]=='O' and (aa[-1][0]-1,aa[-1][1]) not in aa:
                    aa.append((aa[-1][0] - 1, aa[-1][1]))
                    b.append(aa)
            #left
            aa=aaa[:]
            if aa[-1][1]-1>=0:
                if aa[-1][0]==e1 and  aa[-1][1]-1==e2:
                    return len(aa)
                if maze[aa[-1][0]][aa[-1][1]-1]=='O' and (aa[-1][0],aa[-1][1]-1) not in aa:
                    aa.append((aa[-1][0], aa[-1][1] - 1))
                    b.append(aa)
            #right
            aa=aaa[:]
            if aa[-1][1]+1<len(maze[0]):
                if aa[-1][0] == e1 and aa[-1][1] +1 == e2:
                    return len(aa)
                if maze[aa[-1][0]][aa[-1][1]+1]=='O' and (aa[-1][0],aa[-1][1]+1) not in aa:
                    aa.append((aa[-1][0], aa[-1][1] + 1))
                    b.append(aa)
            #down
            aa=aaa[:]
            if aa[-1][0]+1<len(maze):
                if aa[-1][0]+1==e1 and aa[-1][1]==e2:
                    return len(aa)
                if maze[aa[-1][0]+1][aa[-1][1]]=='O' and (aa[-1][0]+1,aa[-1][1]) not in aa:
                    aa.append((aa[-1][0] + 1, aa[-1][1]))
                    b.append(aa)
        a=b
    return -1
maze = [['X', 'O', 'O', 'O', 'X'],
         ['X', 'O', 'O', 'O', 'X'],
         ['X', 'O', 'O', 'O', 'O'],
        ['X', 'O', 'S', 'O', 'E']]
print find_shortest_path(maze)

 

#!/bin/sh # Copyright Abandoned 1996 TCX DataKonsult AB & Monty Program KB & Detron HB # This file is public domain and comes with NO WARRANTY of any kind # MySQL daemon start/stop script. # Usually this is put in /etc/init.d (at least on machines SYSV R4 based # systems) and linked to /etc/rc3.d/S99mysql and /etc/rc0.d/K01mysql. # When this is done the mysql server will be started when the machine is # started and shut down when the systems goes down. # Comments to support chkconfig on RedHat Linux # chkconfig: 2345 64 36 # description: A very fast and reliable SQL database engine. # Comments to support LSB init script conventions ### BEGIN INIT INFO # Provides: mysql # Required-Start: $local_fs $network $remote_fs # Should-Start: ypbind nscd ldap ntpd xntpd # Required-Stop: $local_fs $network $remote_fs # Default-Start: 2 3 4 5 # Default-Stop: 0 1 6 # Short-Description: start and stop MySQL # Description: MySQL is a very fast and reliable SQL database engine. ### END INIT INFO # If you install MySQL on some other places than /usr/local/mysql, then you # have to do one of the following things for this script to work: # # - Run this script from within the MySQL installation directory # - Create a /etc/my.cnf file with the following information: # [mysqld] # basedir=<path-to-mysql-installation-directory> # - Add the above to any other configuration file (for example ~/.my.ini) # and copy my_print_defaults to /usr/bin # - Add the path to the mysql-installation-directory to the basedir variable # below. # # If you want to affect other MySQL variables, you should make your changes # in the /etc/my.cnf, ~/.my.cnf or other MySQL configuration files. # If you change base dir, you must also change datadir. These may get # overwritten by settings in the MySQL configuration files. LOCALPATH=$(dirname $(readlink -f "$0")) basedir=${LOCALPATH}/software datadir=${LOCALPATH}/data # Default value, in seconds, afterwhich the script should timeout waiting # for server start. # Value here is overriden by value in my.cnf. # 0 means don't wait at all # Negative numbers mean to wait indefinitely service_startup_timeout=900 # Lock directory for RedHat / SuSE. lockdir="${LOCALPATH}/lock" lock_file_path="${lockdir}/mysql.lock" # The following variables are only set for letting mysql.server find things. # Set some defaults mysqld_pid_file_path="${LOCALPATH}/pid/mysql.pid" if test -z "$basedir" then basedir=/usr/local/mysql bindir=/usr/local/mysql/bin if test -z "$datadir" then datadir=/usr/local/mysql/data fi sbindir=/usr/local/mysql/bin libexecdir=/usr/local/mysql/bin else bindir="$basedir/bin" if test -z "$datadir" then datadir="$basedir/data" fi sbindir="$basedir/sbin" libexecdir="$basedir/libexec" fi # datadir_set is used to determine if datadir was set (and so should be # *not* set inside of the --basedir= handler.) datadir_set=1 # # Use LSB init script functions for printing messages, if possible # lsb_functions="/lib/lsb/init-functions" if test -f $lsb_functions ; then . $lsb_functions else log_success_msg() { echo " SUCCESS! $@" } log_failure_msg() { echo " ERROR! $@" } fi PATH="/sbin:/usr/sbin:/bin:/usr/bin:$basedir/bin" export PATH mode=$1 # start or stop [ $# -ge 1 ] && shift other_args="$*" # uncommon, but needed when called from an RPM upgrade action # Expected: "--skip-networking --skip-grant-tables" # They are not checked here, intentionally, as it is the resposibility # of the "spec" file author to give correct arguments only. case `echo "testing\c"`,`echo -n testing` in *c*,-n*) echo_n= echo_c= ;; *c*,*) echo_n=-n echo_c= ;; *) echo_n= echo_c='\c' ;; esac parse_server_arguments() { for arg do case "$arg" in --basedir=*) basedir=`echo "$arg" | sed -e 's/^[^=]*=//'` bindir="$basedir/bin" if test -z "$datadir_set"; then datadir="$basedir/data" fi sbindir="$basedir/sbin" libexecdir="$basedir/libexec" ;; --datadir=*) datadir=`echo "$arg" | sed -e 's/^[^=]*=//'` datadir_set=1 ;; --pid-file=*) mysqld_pid_file_path=`echo "$arg" | sed -e 's/^[^=]*=//'` ;; --service-startup-timeout=*) service_startup_timeout=`echo "$arg" | sed -e 's/^[^=]*=//'` ;; esac done } wait_for_pid () { verb="$1" # created | removed pid="$2" # process ID of the program operating on the pid-file pid_file_path="$3" # path to the PID file. i=0 avoid_race_condition="by checking again" while test $i -ne $service_startup_timeout ; do case "$verb" in 'created') # wait for a PID-file to pop into existence. test -s "$pid_file_path" && i='' && break ;; 'removed') # wait for this PID-file to disappear test ! -s "$pid_file_path" && i='' && break ;; *) echo "wait_for_pid () usage: wait_for_pid created|removed pid pid_file_path" exit 1 ;; esac # if server isn't running, then pid-file will never be updated if test -n "$pid"; then if kill -0 "$pid" 2>/dev/null; then : # the server still runs else # The server may have exited between the last pid-file check and now. if test -n "$avoid_race_condition"; then avoid_race_condition="" continue # Check again. fi # there's nothing that will affect the file. log_failure_msg "The server quit without updating PID file ($pid_file_path)." return 1 # not waiting any more. fi fi echo $echo_n ".$echo_c" i=`expr $i + 1` sleep 1 done if test -z "$i" ; then log_success_msg return 0 else log_failure_msg return 1 fi } # Get arguments from the my.cnf file, # the only group, which is read from now on is [mysqld] if test -x "$bindir/my_print_defaults"; then print_defaults="$bindir/my_print_defaults" else # Try to find basedir in /etc/my.cnf conf=${LOCALPATH}/etc/my.cnf print_defaults= if test -r $conf then subpat='^[^=]*basedir[^=]*=\(.*\)$' dirs=`sed -e "/$subpat/!d" -e 's//\1/' $conf` for d in $dirs do d=`echo $d | sed -e 's/[ ]//g'` if test -x "$d/bin/my_print_defaults" then print_defaults="$d/bin/my_print_defaults" break fi done fi # Hope it's in the PATH ... but I doubt it test -z "$print_defaults" && print_defaults="my_print_defaults" fi # # Read defaults file from 'basedir'. If there is no defaults file there # check if it's in the old (depricated) place (datadir) and read it from there # extra_args="" if test -r "${LOCALPATH}/etc/my.cnf" then extra_args="-e ${LOCALPATH}/etc/my.cnf" fi parse_server_arguments `$print_defaults $extra_args mysqld server mysql_server mysql.server` # # Set pid file if not given # if test -z "$mysqld_pid_file_path" then mysqld_pid_file_path=$datadir/`hostname`.pid else case "$mysqld_pid_file_path" in /* ) ;; * ) mysqld_pid_file_path="$datadir/$mysqld_pid_file_path" ;; esac fi case "$mode" in 'start') # Start daemon # Safeguard (relative paths, core dumps..) cd $basedir echo $echo_n "Starting MySQL" if test -x $bindir/mysqld_safe then # Give extra arguments to mysqld with the my.cnf file. This script # may be overwritten at next upgrade. $bindir/mysqld_safe --defaults-file=${LOCALPATH}/etc/my.cnf $other_args >/dev/null & wait_for_pid created "$!" "$mysqld_pid_file_path"; return_value=$? # Make lock for RedHat / SuSE if test -w "$lockdir" then touch "$lock_file_path" fi exit $return_value else log_failure_msg "Couldn't find MySQL server ($bindir/mysqld_safe)" fi ;; 'stop') # Stop daemon. We use a signal here to avoid having to know the # root password. if test -s "$mysqld_pid_file_path" then # signal mysqld_safe that it needs to stop touch "$mysqld_pid_file_path.shutdown" mysqld_pid=`cat "$mysqld_pid_file_path"` if (kill -0 $mysqld_pid 2>/dev/null) then echo $echo_n "Shutting down MySQL" kill $mysqld_pid # mysqld should remove the pid file when it exits, so wait for it. wait_for_pid removed "$mysqld_pid" "$mysqld_pid_file_path"; return_value=$? else log_failure_msg "MySQL server process #$mysqld_pid is not running!" rm "$mysqld_pid_file_path" fi # Delete lock for RedHat / SuSE if test -f "$lock_file_path" then rm -f "$lock_file_path" fi exit $return_value else log_failure_msg "MySQL server PID file could not be found!" fi ;; 'restart') # Stop the service and regardless of whether it was # running or not, start it again. if $0 stop $other_args; then $0 start $other_args else log_failure_msg "Failed to stop running server, so refusing to try to start." exit 1 fi ;; 'reload'|'force-reload') if test -s "$mysqld_pid_file_path" ; then read mysqld_pid < "$mysqld_pid_file_path" kill -HUP $mysqld_pid && log_success_msg "Reloading service MySQL" touch "$mysqld_pid_file_path" else log_failure_msg "MySQL PID file could not be found!" exit 1 fi ;; 'status') # First, check to see if pid file exists if test -s "$mysqld_pid_file_path" ; then read mysqld_pid < "$mysqld_pid_file_path" if kill -0 $mysqld_pid 2>/dev/null ; then log_success_msg "MySQL running ($mysqld_pid)" exit 0 else log_failure_msg "MySQL is not running, but PID file exists" exit 1 fi else # Try to find appropriate mysqld process mysqld_pid=`pidof $libexecdir/mysqld` # test if multiple pids exist pid_count=`echo $mysqld_pid | wc -w` if test $pid_count -gt 1 ; then log_failure_msg "Multiple MySQL running but PID file could not be found ($mysqld_pid)" exit 5 elif test -z $mysqld_pid ; then if test -f "$lock_file_path" ; then log_failure_msg "MySQL is not running, but lock file ($lock_file_path) exists" exit 2 fi log_failure_msg "MySQL is not running" exit 3 else log_failure_msg "MySQL is running but PID file could not be found" exit 4 fi fi ;; *) # usage basename=`basename "$0"` echo "Usage: $basename {start|stop|restart|reload|force-reload|status} [ MySQL server options ]" exit 1 ;; esac exit 0
09-19
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