I have written code for 2 approaches to find out the first unique character in a string on LeetCode.Problem Statement: Given a string, find the first non-repeating character in it and return it's index. If it doesn't exist, return -1.

## data structure with O(1) search time complexity in c++

is there a data structure in c++ that has a search time complexity of O(1)? As in to check if an element is present in it or not, and if present, what its position or associated index/ key/value is

## O(NlogN) algorithm runs faster than O(n)… wait, what?

I am a bit confused, to be honest. I was working out the one of the classical algorithm problems. Given a collection of integers, find if are there 2 elements summing to a given number.

## Why is Regex (c++) taking exponential time?

I'm doing some regex problems from a textbook and of them reads the following:"[Match] all strings that start at the beginning of the line with an integer and that end at the end of the line with a word."

## How std::advance iterator type is deduced?

Please take a look at the std::advance function. According to cppreference the complexity is:Linear. However, if InputIt additionally meets the requirements of RandomAccessIterator, complexity is constant.

## Why is splitting a Rust's std::collections::LinkedList O(n)?

The .split_off method on std::collections::LinkedList is described as having a O(n) time complexity. From the (docs):

## Why Time Complexity is O(n) , not O(nlogn)

I came across this time complexity example online, and am slightly confused. The answer is stated as O(n). I am wondering why it is not O(nlogn). The reason why I say this is because the outer loop looks to be logarithmic, while the inner loop appears to be linear. If...