fd

Author: liwentian

ebook/Backtracking.aux

@@ -71,9 +71,15 @@
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 \@writefile{toc}{\contentsline {subsubsection}{Description}{28}{section*.45}}
 \@writefile{toc}{\contentsline {subsubsection}{Solution}{28}{section*.46}}
+\@writefile{toc}{\contentsline {section}{\numberline {1.21}Word Ladder}{29}{section.1.21}}
+\@writefile{toc}{\contentsline {subsubsection}{Description}{29}{section*.47}}
+\@writefile{toc}{\contentsline {subsubsection}{Solution I}{30}{section*.48}}
+\@writefile{toc}{\contentsline {subsubsection}{Solution II}{31}{section*.49}}
+\@writefile{toc}{\contentsline {section}{\numberline {1.22}Word Ladder II}{32}{section.1.22}}
+\@writefile{toc}{\contentsline {subsubsection}{Description}{32}{section*.50}}
 \FN@pp@footnotehinttrue 
 \@setckpt{Backtracking}{
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@@ -83,20 +89,20 @@
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ebook/Backtracking.tex

@@ -1212,4 +1212,195 @@ \subsubsection{Solution}
 
 \begin{Code}
 
-\end{Code}
+\end{Code}
+
+\newpage
+
+\section{Word Ladder} %%%%%%%%%%%%%%%%%%%%%%
+
+\subsubsection{Description}
+
+Given two words (beginWord and endWord), and a dictionary's word list, find the length of shortest transformation sequence from beginWord to endWord, such that:
+
+Only one letter can be changed at a time.
+
+Each transformed word must exist in the word list. Note that beginWord is not a transformed word.
+
+For example,
+
+Given:
+
+beginWord = \code{"hit"}
+
+endWord = \code{"cog"}
+
+wordList = \code{["hot","dot","dog","lot","log","cog"]}
+
+As one shortest transformation is \code{"hit" -> "hot" -> "dot" -> "dog" -> "cog"},
+
+return its length 5.
+
+\textbf{Note:}
+
+Return 0 if there is no such transformation sequence.
+
+All words have the same length.
+
+All words contain only lowercase alphabetic characters.
+
+You may assume no duplicates in the word list.
+
+You may assume beginWord and endWord are non-empty and are not the same.
+
+\newpage
+
+\subsubsection{Solution I}
+
+\begin{Code}
+/**
+ * 要注意添加节点时要给单词从dict中删掉
+ */
+// 常规的BFS，耗时141ms
+public int ladderLength(String beginWord, String endWord, Set<String> wordList) {
+    wordList.remove(beginWord);
+    wordList.add(endWord);
+
+    Queue<String> queue = new LinkedList<>();
+    Queue<String> next = new LinkedList<>();
+    queue.add(beginWord);
+
+    int ladder = 1;
+
+    while (!queue.isEmpty()) {
+        String word = queue.poll();
+
+        StringBuilder sb = new StringBuilder(word);
+        for (int i = 0; i < word.length(); i++) {
+            char c = word.charAt(i);
+            for (int j = 0; j < 26; j++) {
+                if (j + 'a' == c) {
+                    continue;
+                }
+                sb.setCharAt(i, (char) (j + 'a'));
+                String s = sb.toString();
+
+                if (s.equals(endWord)) {
+                    return ladder + 1;
+                }
+
+                if (wordList.remove(s)) {
+                    next.add(s);
+                }
+            }
+            sb.setCharAt(i, c);
+        }
+
+        if (queue.isEmpty()) {
+            queue.addAll(next);
+            next.clear();
+            ladder++;
+        }
+    }
+
+    return 0;
+}
+\end{Code}
+
+\newpage
+
+\subsubsection{Solution II}
+
+\begin{Code}
+// 采用双端BFS，耗时28ms
+public int ladderLength2(String beginWord, String endWord, Set<String> wordList) {
+    Set<String> beginSet = new HashSet<>();
+    beginSet.add(beginWord);
+
+    Set<String> endSet = new HashSet<String>();
+    endSet.add(endWord);
+
+    int length = 1;
+
+    while (!beginSet.isEmpty() && !endSet.isEmpty()) {
+        if (beginSet.size() > endSet.size()) {
+            Set<String> temp = beginSet;
+            beginSet = endSet;
+            endSet = temp;
+        }
+
+        Set<String> nextSet = new HashSet<String>();
+
+        for (String word : beginSet) {
+            char[] wordArr = word.toCharArray();
+
+            for (int i = 0; i < wordArr.length; i++) {
+                char c = wordArr[i];
+
+                for (int j = 0; j < 26; j++) {
+                    if ('a' + j == c) {
+                        continue;
+                    }
+                    wordArr[i] = (char) ('a' + j);
+                    String s = String.valueOf(wordArr);
+
+                    if (endSet.contains(s)) {
+                        return length + 1;
+                    }
+
+                    if (wordList.contains(s)) {
+                        nextSet.add(s);
+                        wordList.remove(s);
+                    }
+                }
+                wordArr[i] = c;
+            }
+        }
+
+        beginSet = nextSet;
+        length++;
+    }
+
+    return 0;
+}
+\end{Code}
+
+\newpage
+
+\section{Word Ladder II} %%%%%%%%%%%%%%%%%%%%%%
+
+\subsubsection{Description}
+Given two words (beginWord and endWord), and a dictionary's word list, find all shortest transformation sequence(s) from beginWord to endWord, such that:
+
+1. Only one letter can be changed at a time
+
+2. Each transformed word must exist in the word list. Note that beginWord is not a transformed word.
+
+For example,
+
+Given:
+
+beginWord = \code{"hit"}
+
+endWord = \code{"cog"}
+
+wordList = \code{["hot","dot","dog","lot","log","cog"]}
+
+Return
+\begin{Code}
+  [
+    ["hit","hot","dot","dog","cog"],
+    ["hit","hot","lot","log","cog"]
+  ]
+\end{Code}
+
+Note:
+
+Return an empty list if there is no such transformation sequence.
+
+All words have the same length.
+
+All words contain only lowercase alphabetic characters.
+
+You may assume no duplicates in the word list.
+
+You may assume beginWord and endWord are non-empty and are not the same.

ebook/leetcode.log

@@ -1,4 +1,4 @@
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+This is XeTeX, Version 3.14159265-2.6-0.99996 (TeX Live 2016) (preloaded format=xelatex 2017.9.4)  5 SEP 2017 18:08
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@@ -1935,7 +1935,7 @@ File: images/sudoku.png Graphic file (type QTm)
  <use  "images/sudoku.png" >
 File: images/sudoku2.png Graphic file (type QTm)
  <use  "images/sudoku2.png" > [25]
-[26] [27]) [28]
+[26] [27] [28] [29] [30] [31]) [32]
 No file leetcode.ind.
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 Package atveryend Info: Empty hook `AfterLastShipout' on input line 42.
@@ -1947,10 +1947,10 @@ Package atveryend Info: Empty hook `AtVeryVeryEnd' on input line 42.
 Here is how much of TeX's memory you used:
  29203 strings out of 493591
  553766 string characters out of 6143547
- 574513 words of memory out of 5000000
+ 579004 words of memory out of 5000000
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-Output written on leetcode.pdf (30 pages).
+Output written on leetcode.pdf (34 pages).

ebook/leetcode.out

@@ -19,3 +19,5 @@
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ebook/leetcode.pdf

@@ -64,3 +64,9 @@
 \contentsline {section}{\numberline {1.20}Restore IP Addresses}{28}{section.1.20}
 \contentsline {subsubsection}{Description}{28}{section*.45}
 \contentsline {subsubsection}{Solution}{28}{section*.46}
+\contentsline {section}{\numberline {1.21}Word Ladder}{29}{section.1.21}
+\contentsline {subsubsection}{Description}{29}{section*.47}
+\contentsline {subsubsection}{Solution I}{30}{section*.48}
+\contentsline {subsubsection}{Solution II}{31}{section*.49}
+\contentsline {section}{\numberline {1.22}Word Ladder II}{32}{section.1.22}
+\contentsline {subsubsection}{Description}{32}{section*.50}