Math for coding interviews/Constant time - O(1)
O(1) Constant Time, Explained Visually
No matter how large the input is, this operation always takes the same amount of time. The size of n simply does not matter.
See it for yourself
A perfectly flat horizontal line on a graph. The line never rises no matter how far right you go.
Constant time - O(1)
No matter how large the input is, this operation always takes the same amount of time. The size of n simply does not matter.
Think of it this way: Looking up a word in a dictionary if you already know the exact page number. It does not matter how thick the dictionary is.
For algorithms: Accessing array[3] is O(1) because the computer calculates the memory address directly: start + 3 * item_size. One calculation, done.
Real-world analogy
Looking up a word in a dictionary if you already know the exact page number. It does not matter how thick the dictionary is.
Why it matters in interviews
Accessing array[3] is O(1) because the computer calculates the memory address directly: start + 3 * item_size. One calculation, done.