Adding solution of 215, 230, 234, 236, 2338, 239, 240 problems

Author: Garvit244

200-300q/215.py

@@ -0,0 +1,30 @@
+'''
+	Find the kth largest element in an unsorted array. Note that it is the kth largest element in the sorted order, not the kth distinct element.
+
+	Example 1:
+
+	Input: [3,2,1,5,6,4] and k = 2
+	Output: 5
+	Example 2:
+
+	Input: [3,2,3,1,2,4,5,5,6] and k = 4
+	Output: 4
+'''
+
+class Solution(object):
+    def findKthLargest(self, nums, k):
+        """
+        :type nums: List[int]
+        :type k: int
+        :rtype: int
+        """
+        heap = []
+        import heapq
+        for num in nums:
+        	heapq.heappush(heap, -(num))
+
+        result = 0
+        for _ in range(k):
+        	result = heapq.heappop(heap)
+
+        return -(result)

200-300q/230.py

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+'''
+	Given a binary search tree, write a function kthSmallest to find the kth smallest element in it.
+
+	Note: 
+	You may assume k is always valid, 1 ≤ k ≤ BST's total elements.
+
+	Example 1:
+
+	Input: root = [3,1,4,null,2], k = 1
+	Output: 1
+'''
+
+# Definition for a binary tree node.
+# class TreeNode(object):
+#     def __init__(self, x):
+#         self.val = x
+#         self.left = None
+#         self.right = None
+
+class Solution(object):
+    def kthSmallest(self, root, k):
+        """
+        :type root: TreeNode
+        :type k: int
+        :rtype: int
+        """
+        
+        if not root:
+        	return 0
+
+        stack = [root]
+        count, curr = 0, root
+
+
+        while stack:
+        	if curr.left:
+        		stack.append(curr.left)
+        		curr = curr.left
+        	else:
+        		val = stack.pop()
+        		count += 1
+        		if count == k:
+        			return val.val
+
+        		if val.right:
+        			stack.append(val.right)
+        			curr = val.right
+        return float('-inf')

200-300q/234.py

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+# Definition for singly-linked list.
+# class ListNode(object):
+#     def __init__(self, x):
+#         self.val = x
+#         self.next = None
+
+class Solution(object):
+    def isPalindrome(self, head):
+        """
+        :type head: ListNode
+        :rtype: bool
+        """
+        rev = None
+        slow, fast = head, head.next
+        while fast and fast.next:
+        	fast = fast.next.next
+        	temp = slow
+        	slow = slow.next
+        	temp.next = rev
+        	rev = temp
+
+        if fast:
+        	slow = slow.next
+
+        while rev and rev.val == slow.val:
+        	rev = rev.next
+        	slow = slow.next
+        return not rev

200-300q/236.py

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+'''
+	Given a binary tree, find the lowest common ancestor (LCA) of two given nodes in the tree.
+
+	According to the definition of LCA on Wikipedia: “The lowest common ancestor is defined between two nodes v and w as the lowest node in T that has both v and w as descendants (where we allow a node to be a descendant of itself).”
+
+	Given the following binary search tree:  root = [3,5,1,6,2,0,8,null,null,7,4]
+
+	        _______3______
+	       /              \
+	    ___5__          ___1__
+	   /      \        /      \
+	   6      _2       0       8
+	         /  \
+	         7   4
+	Example 1:
+
+	Input: root, p = 5, q = 1
+	Output: 3
+	Explanation: The LCA of of nodes 5 and 1 is 3.
+'''
+
+# Definition for a binary tree node.
+# class TreeNode(object):
+#     def __init__(self, x):
+#         self.val = x
+#         self.left = None
+#         self.right = None
+
+class Solution(object):
+    def lowestCommonAncestor(self, root, p, q):
+        """
+        :type root: TreeNode
+        :type p: TreeNode
+        :type q: TreeNode
+        :rtype: TreeNode
+        """
+        
+        if not root:
+        	return None
+
+        if root == p or root == q:
+        	return root
+
+        l = self.lowestCommonAncestor(root.left, p, q)
+        r = self.lowestCommonAncestor(root.right, p, q)
+
+        if l and r:
+        	return root
+        return l if l else r

200-300q/238.py

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+'''
+	Given an array nums of n integers where n > 1,  return an array output such that output[i] is equal to the product of all the elements of nums except nums[i].
+
+	Example:
+
+	Input:  [1,2,3,4]
+	Output: [24,12,8,6]
+	 1 1 2 6
+	 	12 8 6 
+'''
+
+class Solution(object):
+    def productExceptSelf(self, nums):
+        """
+        :type nums: List[int]
+        :rtype: List[int]
+        """
+        if not nums:
+        	return []
+
+        dp = [1]*len(nums)
+
+        for index in range(1,len(nums)):
+        	dp[index] = dp[index-1]*nums[index-1]
+        print dp
+        right = 1
+        for index in range(len(nums)-1, -1, -1):
+        	dp[index] *= right
+        	right *= nums[index]
+        return dp

200-300q/239.py

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+'''
+	Write an efficient algorithm that searches for a value in an m x n matrix. This matrix has the following properties:
+
+	Integers in each row are sorted in ascending from left to right.
+	Integers in each column are sorted in ascending from top to bottom.
+	Consider the following matrix:
+
+	[
+	  [1,   4,  7, 11, 15],
+	  [2,   5,  8, 12, 19],
+	  [3,   6,  9, 16, 22],
+	  [10, 13, 14, 17, 24],
+	  [18, 21, 23, 26, 30]
+	]
+	Example 1:
+
+	Input: matrix, target = 5
+	Output: true
+'''
+
+class Solution(object):
+    def searchMatrix(self, matrix, target):
+        """
+        :type matrix: List[List[int]]
+        :type target: int
+        :rtype: bool
+        """
+        
+        if not matrix:
+        	return False
+
+        left, right = 0, len(matrix[0])-1
+        while left < len(matrix) and right >= 0:
+        	if matrix[left][right] == target:
+        		return True
+        	elif matrix[left][right] < target:
+        		left += 1
+        	else:
+        		right -= 1
+        return False