Tag Archives: LeetCode

Single Element in a Sorted Array

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Single Element in a Sorted Array. Find the element that appears once in a sorted array where every other element appears twice.

Given a sorted array of integers. In this array, every element appears twice except one element which appears only once. Write a code to find the element which appears only once.

For example:

Example 1:

Input: [1, 1, 2, 2, 3, 4, 4, 7, 7]

Output: 3

Except 3 every other element appears twice.

Example 2:

Input: [1, 1, 2, 2, 3, 3, 4, 5, 5]
Output: 4

NOTE – Try to solve this problem in O(logn) time complexity and by using constant space O(1).

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Get Minimum Element From Stack in O(1)

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Get minimum element from stack in O(1).

In this problem, we have to design a stack that supports push, pop, top, and retrieving the minimum element in constant time (O(1)).

      push(x) — Push element x onto stack.

     pop() — Removes the element on top of the stack.

     top() — Get the top element.

     getMin() — Retrieve the minimum element in the stack.

For example: Suppose, If we push the following elements in a stack.

9  ==> Top
1
2
3

Then if we call getMin() method, It should return 1 in O(1) (constant time).

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How to Check if a Number is a Power of Two

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How to check if a number is a power of two.  Give an integer, write a function to check if it is a power of two.

Example –

Input – 16   – 16 is a power of 2 (2^4).

Input – 15 – 15 is not a power of 2.

Input – 32- 32 is a power of 2 (2^5).

We can use multiple approaches to check whether a number is a power of 2 or not. →