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How does a hash table work?

Q: How does a hash table work?

**Intuition.** A hash table turns a *key* into an *array index* with a hash function, so lookups skip the search entirely — go straight to the slot. That is what gives you average **O(1)** insert and lookup. "cat" hash(key) % size

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hash-table

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Frequency count with a hash map

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def char_count(s):
    counts = {}                       # dict = hash table
    for c in s:
        counts[c] = counts.get(c, 0) + 1
    return counts

print(char_count("banana"))          # {'b':1,'a':3,'n':2}

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