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How do you merge two sorted arrays?

Q: How do you merge two sorted arrays?

**Intuition.** Because both inputs are already sorted, you never need to re-sort — just **walk two pointers** in parallel and always take the smaller current element. This is the *merge* step of merge sort, and it runs in **O(m + n)**. compare heads, take the smaller, advance that pointer 1 <text x="100" y="56" fill="currentCol

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Two-pointer merge

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def merge_sorted(a, b):
    i = j = 0
    out = []
    while i < len(a) and j < len(b):
        if a[i] <= b[j]:
            out.append(a[i]); i += 1
        else:
            out.append(b[j]); j += 1
    out.extend(a[i:])
    out.extend(b[j:])
    return out


# --- demo ---
print(merge_sorted([1, 3, 5], [2, 4, 6]))   # [1, 2, 3, 4, 5, 6]

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