New Problem "Longest Absolute File Path"

Author: haoel

README.md

@@ -8,6 +8,7 @@ LeetCode
 
 | # | Title | Solution | Difficulty |
 |---| ----- | -------- | ---------- |
+[388|[Longest Absolute File Path](https://leetcode.com/problems/longest-absolute-file-path/) | [C++](./algorithms/cpp/longestAbsoluteFilePath/LongestAbsoluteFilePath.cpp)|Medium|
 |387|[First Unique Character in a String](https://leetcode.com/problems/first-unique-character-in-a-string/) | [C++](./algorithms/cpp/firstUniqueCharacterInAString/FirstUniqueCharacterInAString.cpp)|Easy|
 |386|[Lexicographical Numbers](https://leetcode.com/problems/lexicographical-numbers/) | [C++](./algorithms/cpp/lexicographicalNumbers/LexicographicalNumbers.cpp)|Medium|
 |377|[Combination Sum IV](https://leetcode.com/problems/combination-sum-iv/) | [C++](./algorithms/cpp/combinationSumIV/combinationSumIV.cpp)|Medium|

algorithms/cpp/longestAbsoluteFilePath/LongestAbsoluteFilePath.cpp

@@ -0,0 +1,107 @@
+// Source : https://leetcode.com/problems/longest-absolute-file-path/
+// Author : Hao Chen
+// Date   : 2016-08-23
+
+/*************************************************************************************** 
+ *
+ * Suppose we abstract our file system by a string in the following manner:
+ * 
+ * The string "dir\n\tsubdir1\n\tsubdir2\n\t\tfile.ext" represents:
+ * 
+ * dir
+ *     subdir1
+ *     subdir2
+ *         file.ext
+ * 
+ * The directory dir contains an empty sub-directory subdir1 and a sub-directory 
+ * subdir2 containing a file file.ext.
+ * 
+ * The string 
+ * "dir\n\tsubdir1\n\t\tfile1.ext\n\t\tsubsubdir1\n\tsubdir2\n\t\tsubsubdir2\n\t\t\tfile
+ * 2.ext" represents:
+ * 
+ * dir
+ *     subdir1
+ *         file1.ext
+ *         subsubdir1
+ *     subdir2
+ *         subsubdir2
+ *             file2.ext
+ * 
+ * The directory dir contains two sub-directories subdir1 and subdir2. subdir1 contains 
+ * a file file1.ext and an empty second-level sub-directory subsubdir1. subdir2 
+ * contains a second-level sub-directory subsubdir2 containing a file file2.ext.
+ * 
+ * We are interested in finding the longest (number of characters) absolute path to a 
+ * file within our file system. For example, in the second example above, the longest 
+ * absolute path is "dir/subdir2/subsubdir2/file2.ext", and its length is 32 (not 
+ * including the double quotes).
+ * 
+ * Given a string representing the file system in the above format, return the length 
+ * of the longest absolute path to file in the abstracted file system. If there is no 
+ * file in the system, return 0.
+ * 
+ * Note:
+ * 
+ * The name of a file contains at least a . and an extension.
+ * The name of a directory or sub-directory will not contain a ..
+ * 
+ * Time complexity required: O(n) where n is the size of the input string.
+ * 
+ * Notice that a/aa/aaa/file1.txt is not the longest file path, if there is another 
+ * path aaaaaaaaaaaaaaaaaaaaa/sth.png.
+ ***************************************************************************************/
+
+class Solution {
+public:
+    // Solution
+    // --------
+    // We can see the input formation has the order
+    // so, we can maintain an array which states the current level's path length
+    //
+    // For example:
+    //    dir
+    //        subdir1            <- length[ level1 = len("dir")+len("/"), 
+    //                                      level2 = len("dir")+len("/")+len("subdir1")+len("/") ] 
+    //           file.ext
+    //        subdir2
+    //           file.ext
+    //           subsubdir1     <- length[ level1 = len("dir")+len("/"), 
+    //                                     level2 = len("dir")+len("/")+len("subdir2")+len("/"), 
+    //                                     level3 = len("dir")+len("/")+len("subdir2")+len("/")+len("subsubdir1")+len("/") ] 
+    //               file.ext  
+    //
+    int lengthLongestPath(string input) {
+        
+         stringstream ss(input); 
+         string line;
+         int result = 0;
+         
+         vector<int> length;
+         length.push_back(0); //initialize top dummy level's length is zero
+        
+         while (getline(ss, line, '\n')) {
+             //get current level, start from 1
+             int level = 0;
+             while ( line[level++] == '\t'); // get the level
+             int len = line.size() - level + 1;
+
+             //if is a file, then cacualte the total length.
+             if (line.find('.') != string::npos) { 
+                 if ( length[level-1] + len > result ) {
+                    result = length[level-1] + len;
+                 }
+             } else {
+                
+                 if (length.size() <= level) {
+                     length.push_back(0); 
+                 }
+                 
+                 // if it a folder, then update the current level's length
+                 length[level] = length[level-1] + len + 1; // 1 for "/" path delimiter
+             }
+             
+         }
+         return result;
+    }
+};