notebook/notes/hashing/direct-addressing.md

title	TARGET DECK	FILE TAGS	tags
Direct Addressing	Obsidian::STEM	hashing::direct	hashing

Overview

Given a universe of keys U = \{0, 1, \ldots, m - 1\}, a direct-address table has m slots. Each slot corresponds to a key in universe U.

%%ANKI Basic With respect to hashing, what does the "universe" of keys refer to? Back: Every potential key that may be inserted into the underlying dictionary. Reference: Thomas H. Cormen et al., Introduction to Algorithms, Fourth edition (Cambridge, Massachusett: The MIT Press, 2022).

END%%

%%ANKI Basic Given universe U, how many slots must a direct-address table have? Back: |U| Reference: Thomas H. Cormen et al., Introduction to Algorithms, Fourth edition (Cambridge, Massachusett: The MIT Press, 2022).

END%%

%%ANKI Basic What name is given to each position in a direct-address table? Back: A slot. Reference: Thomas H. Cormen et al., Introduction to Algorithms, Fourth edition (Cambridge, Massachusett: The MIT Press, 2022).

END%%

%%ANKI Basic Given a direct-address table, the element at slot k has what key? Back: k. Reference: Thomas H. Cormen et al., Introduction to Algorithms, Fourth edition (Cambridge, Massachusett: The MIT Press, 2022).

END%%

%%ANKI Basic Given a direct-address table, an element with key k is placed in what slot? Back: The $k$th slot. Reference: Thomas H. Cormen et al., Introduction to Algorithms, Fourth edition (Cambridge, Massachusett: The MIT Press, 2022).

END%%

%%ANKI Basic Write pseudocode to test membership of x in direct-address table T[0:m-1]. Back

bool membership(T, x) {
  return T[x.key] != NIL;
}

Reference: Thomas H. Cormen et al., Introduction to Algorithms, Fourth edition (Cambridge, Massachusett: The MIT Press, 2022).

END%%

%%ANKI Basic Write pseudocode to insert x into direct-address table T[0:m-1]. Back

void insert(T, x) {
  T[x.key] = x;
}

Reference: Thomas H. Cormen et al., Introduction to Algorithms, Fourth edition (Cambridge, Massachusett: The MIT Press, 2022).

END%%

%%ANKI Basic Write pseudocode to delete x from direct-address table T[0:m-1]. Back

void delete(T, x) {
  T[x.key] = NIL;
}

Reference: Thomas H. Cormen et al., Introduction to Algorithms, Fourth edition (Cambridge, Massachusett: The MIT Press, 2022).

END%%

Bibliography

• Thomas H. Cormen et al., Introduction to Algorithms, Fourth edition (Cambridge, Massachusett: The MIT Press, 2022).