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LeetCode - Bitwise AND of Numbers Range

Question Definition

Given a range [m, n] where 0 <= m <= n <= 2147483647, return the bitwise AND of all numbers in this range, inclusive.

LeetCode - Binary Number with Alternating Bits

Question Definition

Given a positive integer, check whether it has alternating bits: namely, if two adjacent bits will always have different values.

LeetCode - Simplify Path

Question Definition

Given an absolute path for a file (Unix-style), simplify it.

LeetCode - Verify Preorder Serialization of a Binary Tree

Question Definition

One way to serialize a binary tree is to use pre-order traversal. When we encounter a non-null node, we record the node’s value. If it is a null node, we record using a sentinel value such as #.

     _9_
    /   \
   3     2
  / \   / \
 4   1  #  6
/ \ / \   / \
# # # #   # #

For example, the above binary tree can be serialized to the string “9,3,4,#,#,1,#,#,2,#,6,#,#”, where # represents a null node.

Given a string of comma separated values, verify whether it is a correct preorder traversal serialization of a binary tree. Find an algorithm without reconstructing the tree.

Each comma separated value in the string must be either an integer or a character ‘#’ representing null pointer.

You may assume that the input format is always valid, for example it could never contain two consecutive commas such as “1,,3”.

LeetCode - Remove K Digits

Question Definition

Given a non-negative integer num represented as a string, remove k digits from the number so that the new number is the smallest possible.