Pair With Sum Exists

Hash Mapseasy

Course · Section 9: Data Structures, Modern Operators and Strings · Lecture 124: Maps: Fundamentals

Implement `hasPairWithSum(nums, target)` returning whether two distinct elements add up to `target`, using a set for O(n) lookups.

Input: hasPairWithSum([1,2,3], 5)

Output: true

Input: hasPairWithSum([1,2], 10)

Output: false

+ 1 hidden test run on Submit.

Common pitfalls

Checking the complement before considering distinctness; adding after the check handles it.

Approach & explanation (try first)

A running set lets you check each complement in O(1), giving O(n) time overall.

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