# Posts published in “Easy”

Given two lists Aand B, and B is an anagram of AB is an anagram of A means B is made by randomizing the order of the elements in A.

We want to find an index mapping P, from A to B. A mapping P[i] = j means the ith element in A appears in B at index j.

These lists A and B may contain duplicates. If there are multiple answers, output any of them.

For example, given

We should return

as P = 1 because the 0th element of A appears at B, and P = 4 because the 1st element of Aappears at B, and so on.

Solution:

C++

Time complexity: O(nlogn)

Space complexity: O(n)

C++ / No duplication

Problem:

Given a positive integer, output its complement number. The complement strategy is to flip the bits of its binary representation.

Note:

1. The given integer is guaranteed to fit within the range of a 32-bit signed integer.
2. You could assume no leading zero bit in the integer’s binary representation.

Example 1:

Example 2:

Idea:

Bit

Solution:

C++

Given a positive integer num, write a function which returns True if num is a perfect square else False.

Note: Do not use any built-in library function such as sqrt.

Example 1:

Example 2:

Idea:

Binary search

Solution:

C++

Time complexity: O(log(num))

Space complexity: O(1)

Problem:

Given a Binary Search Tree and a target number, return true if there exist two elements in the BST such that their sum is equal to the given target.

Example 1:

Example 2:

Solution:

C++

Problem:

In a given integer array nums, there is always exactly one largest element.

Find whether the largest element in the array is at least twice as much as every other number in the array.

If it is, return the index of the largest element, otherwise return -1.

Example 1:

Example 2:

Note:

1. nums will have a length in the range [1, 50].
2. Every nums[i] will be an integer in the range [0, 99].

Solution:

C++