diff --git a/200-300q/281.py b/200-300q/281.py
new file mode 100644
index 0000000..0dab44a
--- /dev/null
+++ b/200-300q/281.py
@@ -0,0 +1,35 @@
+'''
+Given two 1d vectors, implement an iterator to return their elements alternately.
+
+For example, given two 1d vectors:
+
+v1 = [1, 2]
+v2 = [3, 4, 5, 6]
+By calling next repeatedly until hasNext returns false, the order of elements returned by next should be: [1, 3, 2, 4, 5, 6].
+'''
+
+class Solution(object):
+	def __init__(self, v1, v2):
+		self.v1 = v1
+		self.v2 = v2
+		self.index_v1 = 0
+		self.index_v2 = 0
+
+	def next(self):
+		result = -1
+		if self.index_v1 != len(self.v1) and self.index_v1 <= self.index_v2:
+			result = self.v1[self.index_v1]
+			self.index_v1 += 1
+		else:
+			result = self.v2[self.index_v2]
+			self.index_v2 += 1
+
+		return result
+
+	def hasNext(self):
+		return self.index_v1 < len(self.v1) or self.index_v2 < len(self.v2)
+
+
+solution = Solution([1, 2], [3, 4, 5, 6])
+while solution.hasNext():
+	print solution.next()
\ No newline at end of file
diff --git a/200-300q/298.py b/200-300q/298.py
new file mode 100644
index 0000000..64fef9f
--- /dev/null
+++ b/200-300q/298.py
@@ -0,0 +1,41 @@
+'''
+Given a binary tree, find the length of the longest consecutive sequence path.
+
+The path refers to any sequence of nodes from some starting node to any node in the tree along the parent-child connections. The longest consecutive path need to be from parent to child (cannot be the reverse).
+
+For example,
+   1
+    \
+     3
+    / \
+   2   4
+        \
+         5
+Longest consecutive sequence path is 3-4-5, so return 3.
+   2
+    \
+     3
+    / 
+   2    
+  / 
+ 1
+Longest consecutive sequence path is 2-3,not3-2-1, so return 2.
+'''
+
+
+class Solution(object):
+	def dfs(curr, parent, length):
+		if not curr:
+			return length
+		if parent:
+			length = length + 1 if curr.val == parent.val + 1
+		else:
+			length = 1
+
+		return max(length, max(dfs(curr.left, curr, length), dfs(curr.right, curr, length)))
+
+	def longestConsecutive(TreeNode root):
+		if not root:
+			return 0
+
+		return dfs(root, null, 0)
diff --git a/300-400q/307.py b/300-400q/307.py
new file mode 100644
index 0000000..9a94600
--- /dev/null
+++ b/300-400q/307.py
@@ -0,0 +1,93 @@
+'''
+Given an integer array nums, find the sum of the elements between indices i and j (i ≤ j), inclusive.
+
+The update(i, val) function modifies nums by updating the element at index i to val.
+
+Example:
+
+Given nums = [1, 3, 5]
+
+sumRange(0, 2) -> 9
+update(1, 2)
+sumRange(0, 2) -> 8
+Note:
+
+The array is only modifiable by the update function.
+You may assume the number of calls to update and sumRange function is distributed evenly.
+'''
+
+class Node(object):
+    def __init__(self, val ,start, end):
+        self.sum = val
+        self.right, self.left = None, None
+        self.range= [start, end]
+        
+class SegementTree(object):
+    def __init__(self, size):
+        self.root = self._build_segment_tree(0, size-1)
+        
+    def _build_segment_tree(self, start, end):
+        if start > end:
+            return None
+        node = Node(0, start, end)
+        if start == end:
+            return node
+        mid = (start+end)/2
+        node.left, node.right = self._build_segment_tree(start, mid), self._build_segment_tree(mid+1, end)
+        return node
+    
+    def update(self, index, val, root=None):
+        root = root or self.root
+        if index < root.range[0] or index > root.range[1]:
+            return
+        root.sum += val
+        if index == root.range[0] == root.range[1]:
+            return 
+        self.update(index, val, root.left)
+        self.update(index, val, root.right)
+            
+    def range_sum(self, start, end, root=None):
+        root = root or self.root
+        if end < root.range[0] or start > root.range[1]:
+            return 0
+        if start <= root.range[0] and end >= root.range[1]:
+            return root.sum
+        return self.range_sum(start, end, root.left) + self.range_sum(start, end, root.right)
+        
+        
+class NumArray(object):
+
+    def __init__(self, nums):
+        """
+        :type nums: List[int]
+        """
+        self.nums = nums
+        self.segment_tree = SegementTree(len(nums))
+        for index, num in enumerate(nums):
+            self.segment_tree.update(index, num)
+        
+
+    def update(self, i, val):
+        """
+        :type i: int
+        :type val: int
+        :rtype: None
+        """
+        diff = val-self.nums[i]
+        self.segment_tree.update(i, diff)
+        self.nums[i] = val
+        
+
+    def sumRange(self, i, j):
+        """
+        :type i: int
+        :type j: int
+        :rtype: int
+        """
+        return self.segment_tree.range_sum(i, j)
+
+
+# Your NumArray object will be instantiated and called as such:
+# obj = NumArray(nums)
+# obj.update(i,val)
+# param_2 = obj.sumRange(i,j)
\ No newline at end of file
diff --git a/300-400q/346.py b/300-400q/346.py
new file mode 100644
index 0000000..4a6b082
--- /dev/null
+++ b/300-400q/346.py
@@ -0,0 +1,33 @@
+'''
+Given a stream of integers and a window size, calculate the moving average of all integers in the sliding window.
+
+For example,
+MovingAverage m = new MovingAverage(3);
+m.next(1) = 1
+m.next(10) = (1 + 10) / 2
+m.next(3) = (1 + 10 + 3) / 3
+m.next(5) = (10 + 3 + 5) / 3
+'''
+
+class Solution(object):
+	def __init__(self):
+		self.queue = []
+		self.curr_sum = 0
+
+	def movingAverage(self, num, size):
+		if len(self.queue) >= size:
+			val = self.queue.pop(0)
+			self.curr_sum -= val
+
+		self.curr_sum += num
+		self.queue.append(num)
+		return float(self.curr_sum)/len(self.queue)
+
+	
+
+solution = Solution()
+window_size = int(input())
+num = int(input())
+while num != -1:
+	print solution.movingAverage(num, window_size)
+	num = int(input())
\ No newline at end of file
diff --git a/400-500Q/418.py b/400-500Q/418.py
new file mode 100644
index 0000000..136f4fc
--- /dev/null
+++ b/400-500Q/418.py
@@ -0,0 +1,80 @@
+'''
+Given a rows x cols screen and a sentence represented by a list of non-empty words, find how many times the given sentence can be fitted on the screen.
+
+Note:
+
+A word cannot be split into two lines.
+The order of words in the sentence must remain unchanged.
+Two consecutive words in a line must be separated by a single space.
+Total words in the sentence won't exceed 100.
+Length of each word is greater than 0 and won't exceed 10.
+1 ≤ rows, cols ≤ 20,000.
+Example 1:
+
+Input:
+rows = 2, cols = 8, sentence = ["hello", "world"]
+
+Output: 
+1
+
+Explanation:
+hello---
+world---
+
+The character '-' signifies an empty space on the screen.
+Example 2:
+
+Input:
+rows = 3, cols = 6, sentence = ["a", "bcd", "e"]
+
+Output: 
+2
+
+Explanation:
+a-bcd- 
+e-a---
+bcd-e-
+
+The character '-' signifies an empty space on the screen.
+Example 3:
+
+Input:
+rows = 4, cols = 5, sentence = ["I", "had", "apple", "pie"]
+
+Output: 
+1
+
+Explanation:
+I-had
+apple
+pie-I
+had--
+
+The character '-' signifies an empty space on the screen.
+'''
+
+class Solution(object):
+	def wordsTyping(self, sentences, rows, cols):
+		""""
+		:sentences List<String>
+		:rows int
+		:cols int
+		"""
+		sentence = '-'.join(sentences)
+		sentence += '-'
+
+		index_in_sentence = 0
+		for row in range(rows):
+			index_in_sentence += cols
+			if sentence[(index_in_sentence%len(sentence))] == '-':
+				index_in_sentence += 1
+			else:
+				while index_in_sentence > 0 and sentence[((index_in_sentence - 1)%len(sentence))] != '-':
+					index_in_sentence -= 1
+
+		return index_in_sentence/len(sentence)
+
+solution = Solution()
+row, col = 3, 6
+sentences = ["a", "bcd", "e"]
+print solution.wordsTyping(sentences=sentences, rows=row, cols=col)
diff --git a/README.md b/README.md
index 8e5a009..61f79ae 100644
--- a/README.md
+++ b/README.md
@@ -97,6 +97,7 @@ Python solution of problems from [LeetCode](https://leetcode.com/).
 |454|[4Sum II](https://leetcode.com/problems/4sum-ii/)|[Python](./400-500Q/454.py)|Medium|
 |448|[Find All Numbers Disappeared in an Array](https://leetcode.com/problems/find-all-numbers-disappeared-in-an-array)|[Python](./400-500q/448.py)|Easy|
 |442|[Find All Duplicates in an Array](https://leetcode.com/problems/find-all-duplicates-in-an-array)|[Python](./400-500q/442.py)|Easy|
+|418|[Sentence Screen Fitting](https://leetcode.com/problems/sentence-screen-fitting)|[Python](./400-500q/418.py)|Medium|
 |410|[Split Array Largest Sum](https://leetcode.com/problems/split-array-largest-sum/) | [Python](./400-500Q/410.py)|Hard|
 
 
@@ -109,6 +110,7 @@ Python solution of problems from [LeetCode](https://leetcode.com/).
 |378|[Kth Smallest Element in a Sorted Matrix](https://leetcode.com/problems/kth-smallest-element-in-a-sorted-matrix) | [Python](./300-400q/378.py)|Medium|
 |350|[Intersection of Two Arrays II](https://leetcode.com/problems/intersection-of-two-arrays-ii/) | [Python](./300-400q/350.py)|Easy|
 |347|[Top K Frequent Elements](https://leetcode.com/problems/top-k-frequent-elements/) | [Python](./300-400q/347.py)|Medium|
+|346|[Moving Average from Data Stream](https://leetcode.com/problems/moving-average-from-data-stream)|[Python](./300-400q/346.py)|Easy|
 |340|[Longest Substring with At Most K Distinct Characters](https://leetcode.com/problems/longest-substring-with-at-most-k-distinct-characters)|[Python](./300-400q/340.py)|Hard|
 |334|[Increasing Triplet Subsequence](https://leetcode.com/problems/increasing-triplet-subsequence/) | [Python](./300-400q/334.py)|Medium|
 |332|[Reconstruct Itinerary](https://leetcode.com/problems/reconstruct-itinerary/)|[Python](./300-400q/332.py)|Medium|
@@ -117,18 +119,21 @@ Python solution of problems from [LeetCode](https://leetcode.com/).
 |326|[Power of Three](https://leetcode.com/problems/power-of-three/) | [Python](./300-400q/326.py)|Easy|
 |322|[Coin Change](https://leetcode.com/problems/coin-change/) | [Python](./300-400q/322.py)|Medium|
 |315|[Count of Smaller Numbers After Self](https://leetcode.com/problems/count-of-smaller-numbers-after-self/) | [Python](./300-400q/315.py)|Hard|
+|307|[Range Sum Query - Mutable](https://leetcode.com/problems/range-sum-query-mutable)|[Python](./300-400q/307.py)|Medium|
 |301|[Remove Invalid Parentheses](https://leetcode.com/problems/remove-invalid-parentheses)|[Python](./300-400q/301.py)|Hard|
 
 ##### [Problems 200-300q](./200-300q/)
 | # | Title | Solution | Difficulty |
 |---| ----- | -------- | ---------- |
 |300|[Longest Increasing Subsequence](https://leetcode.com/problems/longest-increasing-subsequence/)  | [Python](./200-300q/300.py)|Medium|
+|298|[Binary Tree Longest Consecutive Sequence ](https://leetcode.com/problems/binary-tree-longest-consecutive-sequence)|[Python](./200-300q/298.py)|Medium|
 |297|[Serialize and Deserialize Binary Tree](https://leetcode.com/problems/serialize-and-deserialize-binary-tree) | [Python](./200-300q/297.py)|Hard|
 |295|[Find Median from Data Stream](https://leetcode.com/problems/find-median-from-data-stream/) | [Python](./200-300q/295.py)|Hard|
 |289|[Game of Life](https://leetcode.com/problems/game-of-life) | [Python](/200-300q/289.py)|Medium|
 |287|[Find the Duplicate Number](https://leetcode.com/problems/find-the-duplicate-number/)  | [Python](./200-300q/287.py)|Hard|
 |285|[Inorder Successor in BST](https://leetcode.com/problems/inorder-successor-in-bst) | [Python](./200-300q/285.py)|Medium|
 |283|[Move Zeros](https://leetcode.com/problems/move-zeroes)|[Python](./200-300q/283.py)|Easy|
+|281|[Zigzag Iterator](https://leetcode.com/problems/zigzag-iterator)|[Python](./200-300q/281.py)|Medium|
 |279|[Perfect Squares](https://leetcode.com/problems/perfect-squares/) | [Python](./200-300q/279.py)|Medium|
 |268|[Missing Number](https://leetcode.com/problems/missing-number)|[Python](./200-300q/268.py)|Easy|
 |257|[Binary Tree Paths](https://leetcode.com/problems/binary-tree-paths)|[Python](./200-300q/257.py)|Easy|