fd

Author: liwentian

ebook/Backtracking.aux

@@ -62,9 +62,18 @@
 \@writefile{toc}{\contentsline {section}{\numberline {1.17}Subsets II}{24}{section.1.17}}
 \@writefile{toc}{\contentsline {subsubsection}{Description}{24}{section*.39}}
 \@writefile{toc}{\contentsline {subsubsection}{Solution}{24}{section*.40}}
+\@writefile{toc}{\contentsline {section}{\numberline {1.18}Sudoku Solver}{25}{section.1.18}}
+\@writefile{toc}{\contentsline {subsubsection}{Description}{25}{section*.41}}
+\@writefile{toc}{\contentsline {subsubsection}{Solution}{25}{section*.42}}
+\@writefile{toc}{\contentsline {section}{\numberline {1.19}Combinations}{27}{section.1.19}}
+\@writefile{toc}{\contentsline {subsubsection}{Description}{27}{section*.43}}
+\@writefile{toc}{\contentsline {subsubsection}{Solution}{27}{section*.44}}
+\@writefile{toc}{\contentsline {section}{\numberline {1.20}Restore IP Addresses}{28}{section.1.20}}
+\@writefile{toc}{\contentsline {subsubsection}{Description}{28}{section*.45}}
+\@writefile{toc}{\contentsline {subsubsection}{Solution}{28}{section*.46}}
 \FN@pp@footnotehinttrue 
 \@setckpt{Backtracking}{
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@@ -74,20 +83,20 @@
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 }

ebook/Backtracking.tex

@@ -1070,3 +1070,146 @@ \subsubsection{Solution}
     subsetsWithDup(nums, start + 1, list, path);
 }
 \end{Code}
+
+\newpage
+
+\section{Sudoku Solver} %%%%%%%%%%%%%%%%%%%%%%
+
+\subsubsection{Description}
+
+Write a program to solve a Sudoku puzzle by filling the empty cells.
+
+Empty cells are indicated by the character \fn{'.'}.
+
+You may assume that there will be only one unique solution.
+
+\begin{center}
+\includegraphics[width=100pt]{sudoku.png}
+\includegraphics[width=100pt]{sudoku2.png}
+\end{center}
+
+\subsubsection{Solution}
+
+\begin{Code}
+public void solveSudoku(char[][] board) {
+    if (board.length == 0) {
+        return;
+    }
+    solve(board);
+}
+
+private boolean solve(char[][] board) {
+    for (int i = 0; i < board.length; i++) {
+        for (int j = 0; j < board[0].length; j++) {
+            if (board[i][j] == '.') {
+                for (char c = '1'; c <= '9'; c++) {
+                    if (check(board, i, j, c)) {
+                        board[i][j] = c;
+
+                        if (solve(board)) {
+                            return true;
+                        } else {
+                            board[i][j] = '.';
+                        }
+                    }
+                }
+                return false;
+            }
+        }
+    }
+    return true;
+}
+\end{Code}
+
+\newpage
+
+\begin{Code}
+private boolean check(char[][] board, int row, int col, char c) {
+    for (int i = 0; i < 9; i++) {
+        if (board[row][i] == c) {
+            return false;
+        }
+        if (board[i][col] == c) {
+            return false;
+        }
+
+        int m = (row / 3) * 3 + i / 3;
+        int n = (col / 3) * 3 + i % 3;
+
+        if (board[m][n] == c) {
+            return false;
+        }
+    }
+    return true;
+}
+\end{Code}
+
+\newpage
+
+\section{Combinations} %%%%%%%%%%%%%%%%%%%%%%
+
+\subsubsection{Description}
+
+Given two integers n and k, return all possible combinations of k numbers out of 1 ... n.
+
+For example,
+
+If n = 4 and k = 2, a solution is:
+\begin{Code}
+[
+  [2,4],
+  [3,4],
+  [2,3],
+  [1,2],
+  [1,3],
+  [1,4],
+]
+\end{Code}
+
+\subsubsection{Solution}
+
+\begin{Code}
+public List<List<Integer>> combine(int n, int k) {
+    List<List<Integer>> result = new ArrayList<List<Integer>>();
+    List<Integer> path = new ArrayList<Integer>();
+    combine(n, k, result, path, 1);
+    return result;
+}
+
+private void combine(int n, int k, List<List<Integer>> result, List<Integer> path, int start) {
+    if (k == 0) {
+        result.add(new ArrayList<Integer>(path));
+        return;
+    }
+
+    if (start > n) {
+        return;
+    }
+
+    path.add(start);
+    combine(n, k - 1, result, path, start + 1);
+    path.remove(path.size() - 1);
+
+    combine(n, k, result, path, start + 1);
+}
+\end{Code}
+
+\newpage
+
+\section{Restore IP Addresses} %%%%%%%%%%%%%%%%%%%%%%
+
+\subsubsection{Description}
+
+Given a string containing only digits, restore it by returning all possible valid IP address combinations.
+
+For example:
+
+Given \code{"25525511135"},
+
+return \code{["255.255.11.135", "255.255.111.35"]}. (Order does not matter)
+
+\subsubsection{Solution}
+
+\begin{Code}
+
+\end{Code}

ebook/images/sudoku.png

@@ -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 17:54
 entering extended mode
  restricted \write18 enabled.
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@@ -1930,7 +1930,12 @@ and I'll forget about whatever was undefined.
 [14] [15] [16] [17] [18]
 File: images/8-queens.png Graphic file (type QTm)
  <use  "images/8-queens.png" > [19] [20] [21] [22]
-[23]) [24]
+[23] [24]
+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]
 No file leetcode.ind.
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@@ -1940,12 +1945,12 @@ Package atveryend Info: Empty hook `AtEndAfterFileList' on input line 42.
 Package atveryend Info: Empty hook `AtVeryVeryEnd' on input line 42.
  ) 
 Here is how much of TeX's memory you used:
- 29199 strings out of 493591
- 553710 string characters out of 6143547
- 576323 words of memory out of 5000000
- 32223 multiletter control sequences out of 15000+600000
+ 29203 strings out of 493591
+ 553766 string characters out of 6143547
+ 574513 words of memory out of 5000000
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  1347 hyphenation exceptions out of 8191
  65i,11n,77p,10414b,603s stack positions out of 5000i,500n,10000p,200000b,80000s
 
-Output written on leetcode.pdf (26 pages).
+Output written on leetcode.pdf (30 pages).

ebook/images/sudoku2.png

@@ -16,3 +16,6 @@
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ebook/leetcode.log

@@ -55,3 +55,12 @@
 \contentsline {section}{\numberline {1.17}Subsets II}{24}{section.1.17}
 \contentsline {subsubsection}{Description}{24}{section*.39}
 \contentsline {subsubsection}{Solution}{24}{section*.40}
+\contentsline {section}{\numberline {1.18}Sudoku Solver}{25}{section.1.18}
+\contentsline {subsubsection}{Description}{25}{section*.41}
+\contentsline {subsubsection}{Solution}{25}{section*.42}
+\contentsline {section}{\numberline {1.19}Combinations}{27}{section.1.19}
+\contentsline {subsubsection}{Description}{27}{section*.43}
+\contentsline {subsubsection}{Solution}{27}{section*.44}
+\contentsline {section}{\numberline {1.20}Restore IP Addresses}{28}{section.1.20}
+\contentsline {subsubsection}{Description}{28}{section*.45}
+\contentsline {subsubsection}{Solution}{28}{section*.46}