LeetCode 1540. K 次操作转变字符串 哈希

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|                                                                           |
|                          Bash History Cheat Sheet                         |
|                                                                           |
‘---------------------------------------------------------------------v1.12-‘
| Created by Peter Krumins (peter@catonmat.net, @pkrumins on twitter)       |
| www.catonmat.net -- good coders code, great coders reuse                  |
|                                                                           |
| Released under the GNU Free Document License                              |
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 ===================== Emacs Keyboard Shortcut Summary =====================

.--------------.------------------------------------------------------------.
|              |                                                            |
| Shortcut     | Description                                                |
|              |                                                            |
‘--------------+------------------------------------------------------------‘
| C-p          | Fetch the previous command from the history list.          |
‘--------------+------------------------------------------------------------‘
| C-n          | Fetch the next command from the history list.              |
‘--------------+------------------------------------------------------------‘
| M-<          | Move to the first line in the history.                     | 
‘--------------+------------------------------------------------------------‘
| M->          | Move to the end of the input history.                      |
‘--------------+------------------------------------------------------------‘
| C-r          | Search backward starting at the current line (incremental) |
‘--------------+------------------------------------------------------------‘
| C-s          | Search forward starting at the current line (incremental). |
‘--------------+------------------------------------------------------------‘
| M-p          | Search backward using non-incremental search.              |
‘--------------+------------------------------------------------------------‘
| M-n          | Search forward using non-incremental search                |
‘--------------‘------------------------------------------------------------‘

 ======================= Vi Keyboard Shortcut Summary ======================

.--------------.------------------------------------------------------------.
|              |                                                            |
| Shortcut     | Description                                                |
|              |                                                            |
‘--------------+------------------------------------------------------------‘
| k            | Fetch the previous command from the history list.          |
‘--------------+------------------------------------------------------------‘
| j            | Fetch the next command from the history list.              |
‘--------------+------------------------------------------------------------‘
| /string or   | Search history backward for a command matching string.     |
| CTRL-r       |                                                            |
‘--------------+------------------------------------------------------------‘
| ?string or   | Search history forward for a command matching string.      |
| CTRL-s       | (Note that on most machines Ctrl-s STOPS the terminal      |
|              | output, change it with `stty‘ (Ctrl-q to resume)).         |
‘--------------+------------------------------------------------------------‘
| n            | Repeat search in the same direction as previous.           |
‘--------------+------------------------------------------------------------‘
| N            | Repeat search in the opposite direction as previous.       |
‘--------------+------------------------------------------------------------‘
| G            | Move to history line N (for example, 15G).                 |
‘--------------‘------------------------------------------------------------‘

 ======================== History Expansion Summary ========================
 
 Event Designators:

.--------------.------------------------------------------------------------.
|              |                                                            |
| Designator   | Description                                                |
|              |                                                            |
‘--------------+------------------------------------------------------------‘
| !            | Start a history substitution.                              |
‘--------------+------------------------------------------------------------‘
| !!           | Refer to the last command.                                 |
‘--------------+------------------------------------------------------------‘
| !n           | Refer to the n-th command line (try `history‘ command).    |
‘--------------+------------------------------------------------------------‘
| !-n          | Refer to the current command line minus n.                 |
‘--------------+------------------------------------------------------------‘
| !string      | Refer to the most recent command starting with ‘string‘.   |
‘--------------+------------------------------------------------------------‘
| !?string?    | Refer to the most recent command containing ‘string‘.      |
‘--------------+------------------------------------------------------------‘
| ^str1^str2^  | Quick substitution. Repeat the last command, replacing     |
|              | ‘str1‘ with ‘str2‘.                                        |
‘--------------+------------------------------------------------------------‘
| !#           | Refer to the entire command line typed so far.             |
‘--------------‘------------------------------------------------------------‘

 Word Designators:
 (Word designators follow the event designators, separated by a collon ‘:‘)

.--------------.------------------------------------------------------------.
|              |                                                            |
| Designator   | Description                                                |
|              |                                                            |
‘--------------+------------------------------------------------------------‘
| 0            | The zeroth (first) word in a line (usually command name).  |
‘--------------+------------------------------------------------------------‘
| n            | The n-th word in a line.                                   |
‘--------------+------------------------------------------------------------‘
| ^            | The first argument (the second word) in a line.            |
‘--------------+------------------------------------------------------------‘
| $            | The last argument in a line.                               |
‘--------------+------------------------------------------------------------‘
| %            | The word matched by the most recent string search.         |
‘--------------+------------------------------------------------------------‘
| x-y          | A range of words from x to y (-y is synonymous with 0-y).  |
‘--------------+------------------------------------------------------------‘
| *            | All words but the zeroth (synonymous with 1-$).            |
‘--------------+------------------------------------------------------------‘
| x*           | Synonymous with x-$                                        |
‘--------------+------------------------------------------------------------‘
| x-           | The words from x to the second to last word.               |
‘--------------‘------------------------------------------------------------‘

 Modifiers (modifiers follow word designators, separated by a colon):

.--------------.------------------------------------------------------------.
|              |                                                            |
| Modifier     | Description                                                |
|              |                                                            |
‘--------------+------------------------------------------------------------‘
| h            | Remove a trailing pathname component, leaving the head.    |
‘--------------+------------------------------------------------------------‘
| t            | Remove all leading pathname component, leaving the tail.   |
‘--------------+------------------------------------------------------------‘
| r            | Remove a trailing suffix of the form .xxx, leaving the     |
|              | basename.                                                  |
‘--------------+------------------------------------------------------------‘
| e            | Remove all but the trailing suffix.                        |
‘--------------+------------------------------------------------------------‘
| p            | Print the resulting command but do not execute it.         |
‘--------------+------------------------------------------------------------‘
| q            | Quotes the substituted words, escaping further             |
|              | substitutions.                                             |
‘--------------+------------------------------------------------------------‘
| x            | Quotes the substituted words, breaking them into words at  |
|              | blanks and newlines.                                       |
‘--------------+------------------------------------------------------------‘
| s/old/new/   | Substitutes ‘new‘ for ‘old‘.                               |
‘--------------+------------------------------------------------------------‘
| &            | Repeats the previous substitution.                         |
‘--------------+------------------------------------------------------------‘
| g            | Causes s/old/new/ or & to be applied over the entire       |
|              | event line.                                                |
‘--------------‘------------------------------------------------------------‘

 ============ History Behavior Modification via Shell Variables ============

.----------------.----------------------------------------------------------.
|                |                                                          |
| Shell Variable | Description                                              |
|                |                                                          |
‘----------------+----------------------------------------------------------‘
| HISTFILE       | Controls where the history file gets saved.              |
|                | Set to /dev/null not to save the history.                |
|                | Default: ~/.bash_history                                 |
‘----------------+----------------------------------------------------------‘
| HISTFILESIZE   | Controls how many history commands to keep in HISTFILE   |
|                | Default: 500                                             |
‘----------------+----------------------------------------------------------‘
| HISTSIZE       | Controls how many history commands to keep in the        |
|                | history list of current session.                         |
|                | Default: 500                                             |
‘----------------+----------------------------------------------------------‘
| HISTIGNORE     | Controls which commands to ignore and not save to the    |
|                | history list. The variable takes a list of               |
|                | colon separated values. Pattern & matches the previous   |
|                | history command.                                         |
‘----------------‘----------------------------------------------------------‘

 ============ History Behavior Modification via `shopt‘ Command ============

.----------------.----------------------------------------------------------.
|                |                                                          |
| shopt Option   | Description                                              |
|                |                                                          |
‘----------------+----------------------------------------------------------‘
| histappend     | Setting the variable appends current session history to  |
|                | HISTFILE. Unsetting overwrites the file each time.       |
‘----------------+----------------------------------------------------------‘
| histreedit     | If set, puts a failed history substitution back on the   |
|                | command line for re-editing.                             |
‘----------------+----------------------------------------------------------‘
| histverify     | If set, puts the command to be executed after a          |
|                | substitution on command line as if you had typed it.     |
‘----------------‘----------------------------------------------------------‘

 shopt options can be set by a `shopt -s option‘ and
 can be unset by             a `shopt -u option‘.

 =============================== Examples ==================================

 $ echo a b c d e    (executes `echo ab c d e`)
 a b c d e

 $ echo !!:3-$       (executes `echo c d e`)
 c d e

 $ echo !-2:*:q      (executes `echo ‘a b c d e‘`)
 a b c d e

 $ echo !-3:1:2:4:x  (executes `echo ‘a‘ ‘b‘ ‘d‘`)
 a b d

 $ echo !-4:1-3:s/a/foo/:s/b/bar/:s/c/baz/ (executes `echo foo bar baz`)
 foo bar baz

 $ tar -xzf package-x.y.z.tgz
 ...
 $ cd !-1:$:r        (executes `cd package-x.y.z`)
 package-x.y.z $
 
 $ ls -a /tmp
 file1  file2  file3 ...

 $ ^-a^-l^           (executes `ls -l /tmp`)
 -rw-------  1  user  user  file1
 ...

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.---------------------------------------------------------------------------.
| Created by Peter Krumins (peter@catonmat.net, @pkrumins on twitter)       |
| www.catonmat.net -- good coders code, great coders reuse                  | 
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