Merge pull request haoel#83 from Vally79/master

added binaryTreePaths and h-Index_II

Author: Vally79

README.md

@@ -3,7 +3,7 @@ LeetCode
 
 ###LeetCode Algorithm
 
-(Notes: "♥" means you need buy a book from Leetcode)
+(Notes: "♥" means you need to buy a book from Leetcode)
 
 
 | # | Title | Solution | Difficulty |
@@ -15,12 +15,14 @@ LeetCode
 |283|[Move Zeroes](https://leetcode.com/problems/move-zeroes/)  | [C++](./algorithms/cpp/moveZeroes/moveZeroes.cpp)|Easy|
 |279|[Perfect Squares](https://leetcode.com/problems/perfect-squares/) | [C++](./algorithms/cpp/perfectSquares/PerfectSquares.cpp)|Medium|
 |278|[First Bad Version](https://leetcode.com/problems/first-bad-version/)| [C++](./algorithms/cpp/firstBadVersion/FirstBadVersion.cpp), [Java](./algorithms/java/src/firstBadVersion/firstBadVersion.java)|Easy|
+|275|[H-Index II](https://leetcode.com/problems/h-index-ii/)| [C++](./algorithms/cpp/h-Index/h-Index_II.cpp)|Medium|
 |274|[H-Index](https://leetcode.com/problems/h-index/)| [C++](./algorithms/cpp/h-Index/h-Index.cpp)|Medium|
 |273|[Integer to English Words](https://leetcode.com/problems/integer-to-english-words/)| [C++](./algorithms/cpp/integerToEnglishWords/IntegerToEnglishWords.cpp)|Medium|
 |268|[Missing Number](https://leetcode.com/problems/missing-number/)| [C++](./algorithms/cpp/missingNumber/MissingNumber.cpp)|Medium|
 |264|[Ugly Number II](https://leetcode.com/problems/ugly-number-ii/)| [C++](./algorithms/cpp/uglyNumber/UglyNumber.II.cpp)|Medium|
 |263|[Ugly Number](https://leetcode.com/problems/ugly-number/)| [C++](./algorithms/cpp/uglyNumber/UglyNumber.cpp)|Easy|
 |258|[Add Digits](https://leetcode.com/problems/add-digits/)| [C++](./algorithms/cpp/addDigits/addDigits.cpp)|Easy|
+|257|[Binary Tree Paths](https://leetcode.com/problems/binary-tree-paths/)| [C++](./algorithms/cpp/binaryTreePaths/binaryTreePaths.cpp)|Easy|
 |242|[Valid Anagram](https://leetcode.com/problems/valid-anagram/)| [C++](./algorithms/cpp/anagrams/ValidAnagram.cpp)|Easy|
 |241|[Different Ways to Add Parentheses](https://leetcode.com/problems/different-ways-to-add-parentheses/)|[C++](./algorithms/cpp/differentWaysToAddParentheses/DifferentWaysToAddParentheses.cpp)|Medium|
 |240|[Search a 2D Matrix II](https://leetcode.com/problems/search-a-2d-matrix-ii/)|[C++](./algorithms/cpp/search2DMatrix/search2DMatrix.II.cpp)|Medium|

algorithms/cpp/binaryTreePaths/binaryTreePaths.cpp

@@ -0,0 +1,59 @@
+// Source : https://leetcode.com/problems/binary-tree-paths/
+// Author : Calinescu Valentin
+// Date   : 2015-10-23
+
+/*************************************************************************************** 
+ *
+ * Given a binary tree, return all root-to-leaf paths.
+ * 
+ * For example, given the following binary tree:
+ * 
+ *    1
+ *  /   \
+ * 2     3
+ *  \
+ *   5
+ * 
+ * All root-to-leaf paths are:
+ * ["1->2->5", "1->3"]
+ * 
+ * Credits:
+ * Special thanks to @jianchao.li.fighter for adding this problem and creating all test 
+ * cases.
+ *               
+ ***************************************************************************************/
+/**
+ * Definition for a binary tree node.
+ * struct TreeNode {
+ *     int val;
+ *     TreeNode *left;
+ *     TreeNode *right;
+ *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
+ * };
+ */
+class Solution {
+public:
+    vector<string> TreePaths;
+    void DFS(TreeNode* node, string answer)
+    {
+        answer += "->" + to_string(node->val);
+        if(node->left == NULL && node->right == NULL)
+            TreePaths.push_back(answer);
+        else
+        {
+            if(node->left != NULL)
+                DFS(node->left, answer);
+            if(node->right != NULL)
+                DFS(node->right, answer);
+        }
+    }
+    vector<string> binaryTreePaths(TreeNode* root) {
+        if(root != NULL)
+        {
+            DFS(root, "");
+            for(int i = 0; i < TreePaths.size(); i++)
+                TreePaths[i].erase(TreePaths[i].begin(), TreePaths[i].begin() + 2);
+        }
+        return TreePaths;
+    }
+};

algorithms/cpp/h-Index/h-Index_II.cpp

@@ -0,0 +1,36 @@
+// Source : https://leetcode.com/problems/h-index-ii/
+// Author : Calinescu Valentin
+// Date   : 2015-10-23
+
+/*************************************************************************************** 
+ *
+ * Follow up for H-Index: What if the citations array is sorted in ascending order?
+ * Could you optimize your algorithm?
+ *               
+ ***************************************************************************************/
+
+
+
+/* 
+ * Solutions
+ * =========
+ *
+ * At every step we need to check whether this element is not less than
+ * the remaining number of elements bigger than it(including itself) and all the values of
+ * the other elements smaller than it are not more than that number. The h_index is this
+ * number of elements bigger than it(including itself).
+ * 
+ * Time Complexity: O(N)
+ * Space Complexity: O(1)
+ * 
+ */
+class Solution {
+public:
+    int hIndex(vector<int>& citations) {
+        int h_index = 0;
+        for(int i = citations.size() - 1; i >= 0; i--)
+            if(citations[i] >= citations.size() - i && (i - 1 < 0 || citations[i - 1] <= citations.size() - i))
+                h_index = citations.size() - i;
+        return h_index;
+    }
+};