Two Sum: First Pair
Beginner
Find two different positions i < j with nums[i] + nums[j] == target and return [i, j].
If several pairs work, return the one with the smallest i, and among those the smallest j. If no pair works, return [-1, -1].
The starter code checks every pair. It is correct but too slow for long lists. Make it fast.
Examples
Example 1
Input:
two_sum_first_pair([1, 6, 5, 3, 8], 9)
Output:
[0, 4]
1 + 8 (positions 0 and 4) and 6 + 3 (positions 1 and 3) both work. The first has the smaller i.
Example 2
Input:
two_sum_first_pair([2, 4], 7)
Output:
[-1, -1]
No pair adds to 7.
Constraints
0 <= len(nums) <= 2 * 10**50 <= nums[i] <= 10**9-1 <= target <= 2 * 10**9
Theory
Go to TheoryKeywords
dsa-sheetarraysarray-patterns
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