DSA · Theory

Hash Table

Theory

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If you can teach Hash Table using name → phone, you know it. If you only know the heading, you don’t.

Keep Hash Table small. Asha should finish name → phone in a few lines, not a 40-line dump.

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

Use Hash Table when name → phone must stay clear. If a simpler DSA step works, use that instead.

Hash Table miss — bad hash → pile-up. Fix it before you talk about advanced DSA.

After Hash Table, Asha should still remember bad hash → pile-up.

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

Exam tip

For Hash Table: definition + a diary + one failure.

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

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