DSA · Theory

Hashing using the Polynomial Rolling Hash()

Theory

670/810

Hashing using the Polynomial Rolling Hash()

Hashing using the Polynomial Rolling Hash() (string function) is a DSA topic. In plain words you use it for name → phone in a diary. Don’t start with a slogan — start with that picture.

Smallest example: key % size + collision plan. Type it, run it, and say what you see. If you can do that from memory, you know Hashing using the Polynomial Rolling Hash() (string function).

From the example next to this theory: Hashing using the Polynomial Rolling Hash() (string function) — hash maps give average O(1) insert/lookup — dict in Python.

Trap — bad hash → pile-up. Fix that before you talk about advanced DSA.

Viva: what is Hashing using the Polynomial Rolling Hash() (string function)? Then show key % size + collision plan. Then name the trap.

Exam tip

What is Hashing using the Polynomial Rolling Hash() (string function)? Show this: key % size + collision plan. Trap: bad hash → pile-up.

Example

freq = {}
for ch in "banana":
    freq[ch] = freq.get(ch, 0) + 1
print(freq)
print(freq.get("a"), freq.get("z", 0))

Hashing using the Polynomial Rolling Hash() (string function) — hash maps give average O(1) insert/lookup — dict in Python.

Short notes

DefHashing using the Polynomial Rolling Hash() (string function) — name → phone in a diary.
Rulekey % size + collision plan
Trapbad hash → pile-up
Usea diary

DSA · Theory

Hashing using the Polynomial Rolling Hash()

← All stacks

Theory

670/810

Hashing using the Polynomial Rolling Hash()

Hashing using the Polynomial Rolling Hash() (string function) is a DSA topic. In plain words you use it for name → phone in a diary. Don’t start with a slogan — start with that picture.

Smallest example: key % size + collision plan. Type it, run it, and say what you see. If you can do that from memory, you know Hashing using the Polynomial Rolling Hash() (string function).

From the example next to this theory: Hashing using the Polynomial Rolling Hash() (string function) — hash maps give average O(1) insert/lookup — dict in Python.

Trap — bad hash → pile-up. Fix that before you talk about advanced DSA.

Viva: what is Hashing using the Polynomial Rolling Hash() (string function)? Then show key % size + collision plan. Then name the trap.

Exam tip

What is Hashing using the Polynomial Rolling Hash() (string function)? Show this: key % size + collision plan. Trap: bad hash → pile-up.

Example

freq = {}
for ch in "banana":
    freq[ch] = freq.get(ch, 0) + 1
print(freq)
print(freq.get("a"), freq.get("z", 0))

Hashing using the Polynomial Rolling Hash() (string function) — hash maps give average O(1) insert/lookup — dict in Python.

Short notes

DefHashing using the Polynomial Rolling Hash() (string function) — name → phone in a diary.
Rulekey % size + collision plan
Trapbad hash → pile-up
Usea diary

Hashing using the Polynomial Rolling Hash()

Example

Short notes

Questions

Hashing using the Polynomial Rolling Hash()

Example

Short notes

Questions