Two Sum

Problem Return the indices of the two numbers in an array that sum to a given goal. Exactly one valid pair exists.

Input / Output

• Input: integer array nums, integer goal.
• Output: the pair of indices [i, j] with nums[i] + nums[j] == goal.

Constraints

• 2 <= n <= 10^4; exactly one solution; an element may not be reused.

Example

• [1,3,6,7,9], goal = 10 → [1,3] (3 + 7 = 10).