Computer Science

In computer science, recursion refers to a technique where a function solves a problem by calling itself on a smaller input. It matters because the same idea reappears across many later topics, so building a clear mental picture of it early saves a lot of time.

Start from the definition: recursion refers to a technique where a function solves a problem by calling itself on a smaller input. Then define the base case first, then express the general case in terms of it. Follow that same order every time and most questions on this topic become mechanical rather than intimidating.

The short version: recursion refers to a technique where a function solves a problem by calling itself on a smaller input. A quick example makes it concrete — Factorial of 5 unfolds as 5 × 4 × 3 × 2 × 1 = 120.

In computer science, time complexity refers to a measure of how an algorithm's running time grows with input size. It matters because the same idea reappears across many later topics, so building a clear mental picture of it early saves a lot of time.

Start from the definition: time complexity refers to a measure of how an algorithm's running time grows with input size. Then count the dominant repeated operation and express it in Big O notation. Follow that same order every time and most questions on this topic become mechanical rather than intimidating.

The short version: time complexity refers to a measure of how an algorithm's running time grows with input size. A quick example makes it concrete — A single nested loop over n items runs in O(n²) time.

In computer science, arrays and linked lists refers to two core ways of storing sequences, one contiguous and one linked by pointers. It matters because the same idea reappears across many later topics, so building a clear mental picture of it early saves a lot of time.

Start from the definition: arrays and linked lists refers to two core ways of storing sequences, one contiguous and one linked by pointers. Then compare access, insertion and deletion cost for the operation you need most. Follow that same order every time and most questions on this topic become mechanical rather than intimidating.

The short version: arrays and linked lists refers to two core ways of storing sequences, one contiguous and one linked by pointers. A quick example makes it concrete — Arrays give O(1) indexing, while linked lists give O(1) insertion at a known node.

In computer science, binary search refers to an algorithm that halves a sorted search space on every comparison. It matters because the same idea reappears across many later topics, so building a clear mental picture of it early saves a lot of time.

Start from the definition: binary search refers to an algorithm that halves a sorted search space on every comparison. Then check the middle element, discard the impossible half, then repeat. Follow that same order every time and most questions on this topic become mechanical rather than intimidating.

The short version: binary search refers to an algorithm that halves a sorted search space on every comparison. A quick example makes it concrete — Searching 1024 sorted items takes at most about 10 comparisons.

In computer science, object oriented programming refers to organising code around objects that bundle data with the behaviour acting on it. It matters because the same idea reappears across many later topics, so building a clear mental picture of it early saves a lot of time.

Start from the definition: object oriented programming refers to organising code around objects that bundle data with the behaviour acting on it. Then identify entities, give them attributes and methods, then use inheritance for shared behaviour. Follow that same order every time and most questions on this topic become mechanical rather than intimidating.

The short version: object oriented programming refers to organising code around objects that bundle data with the behaviour acting on it. A quick example makes it concrete — A Car class can extend a Vehicle class and reuse its start method.

In computer science, SQL joins refers to operations that combine rows from two tables based on a matching column. It matters because the same idea reappears across many later topics, so building a clear mental picture of it early saves a lot of time.

Start from the definition: SQL joins refers to operations that combine rows from two tables based on a matching column. Then choose inner, left, right or full depending on which unmatched rows must survive. Follow that same order every time and most questions on this topic become mechanical rather than intimidating.

The short version: SQL joins refers to operations that combine rows from two tables based on a matching column. A quick example makes it concrete — An inner join of Orders and Customers returns only orders with a matching customer.

In computer science, pointers and memory refers to variables that store addresses, allowing direct access to memory locations. It matters because the same idea reappears across many later topics, so building a clear mental picture of it early saves a lot of time.

Start from the definition: pointers and memory refers to variables that store addresses, allowing direct access to memory locations. Then draw the memory layout, then follow each arrow before dereferencing. Follow that same order every time and most questions on this topic become mechanical rather than intimidating.

The short version: pointers and memory refers to variables that store addresses, allowing direct access to memory locations. A quick example makes it concrete — Incrementing an int pointer moves it forward by the size of one int.

In computer science, sorting algorithms refers to methods for arranging data in order, differing in speed and memory use. It matters because the same idea reappears across many later topics, so building a clear mental picture of it early saves a lot of time.

Start from the definition: sorting algorithms refers to methods for arranging data in order, differing in speed and memory use. Then match the algorithm to the data size and whether stability matters. Follow that same order every time and most questions on this topic become mechanical rather than intimidating.

The short version: sorting algorithms refers to methods for arranging data in order, differing in speed and memory use. A quick example makes it concrete — Merge sort runs in O(n log n) and is stable; quicksort is faster in practice but not stable.