Two Sum Practice | Dataford Interview Questions

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Problem

A Macy's cart validation service receives item prices and a target promotional budget. Return the indices of the two distinct items whose prices add exactly to the target.

Formal Specification

Implement two_sum(prices, target).

prices is a list of integers, where prices[i] is the price of the item at index i.
target is an integer promotional budget.
Return a list [i, j] where i != j and prices[i] + prices[j] == target.
Return indices in ascending discovery order: the earlier matching index first.
Each valid input has exactly one solution. An item cannot be used twice.

Constraints

2 <= len(prices) <= 100,000
-1,000,000,000 <= prices[i] <= 1,000,000,000
-1,000,000,000 <= target <= 1,000,000,000
Exactly one valid pair exists
An index may not be used more than once

Function Signature

def two_sum(prices, target):