def find_target_pair(nums: list[int], target: int) -> list[int]:
    """Finds two indices with sum == target in O(n) time."""
    seen_map: dict[int, int] = {}
    
    for current_index, value in enumerate(nums):
        complement = target - value
        if complement in seen_map:
            return [seen_map[complement], current_index]
        seen_map[value] = current_index
        
    return []  # No solution found