DSA · Theory

Hashing

Theory

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Hashing is a DSA idea you prove with name → phone, not with a slogan.

Do Hashing once by hand. key % size + collision plan. Change one input. Say the new result out loud.

Without Hashing, a diary gets messy and name → phone is hard to trust.

Riya ships Hashing in a diary. That is the use case worth saying.

If name → phone breaks under Hashing, check bad hash → pile-up first.

After Hashing, Riya should still remember bad hash → pile-up.

Viva for Hashing — what it is → key % size + collision plan → the mistake (bad hash → pile-up).

Exam tip

Board: name → phone. Dry-run Hashing. Name the trap: bad hash → pile-up.

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

Hashing — hash maps give average O(1) insert/lookup — dict in Python.