Q20: Two Sum II (Input Array Is Sorted). - DSA Patterns (Multi-Lang)

In Simple Words: Left pointer at 0, right pointer at $N-1$. If nums[l] + nums[r] < target, increment l; if greater, decrement r.

Time: $O(N)$ | Space: $O(1)$

Multi-Language SolutionsPython 3 • JavaScript • TypeScript • Java • C++

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def twoSum(numbers: list[int], target: int) -> list[int]:
    l, r = 0, len(numbers) - 1
    while l < r:
        curr = numbers[l] + numbers[r]
        if curr == target:
            return [l + 1, r + 1]  # 1-indexed
        elif curr < target:
            l += 1
        else:
            r -= 1
    return []