How should I practice Two Sum?

Start by reading the full statement, solve the visible examples, then compare the pattern against related BNSF Railway phone screen problems in FastPrep.

Is Two Sum associated with BNSF Railway?

FastPrep tags this as a BNSF Railway phone screen coding practice problem when the problem catalog has that company and stage context.

Two Sum

BNSF Railway● EasyFULLTIMEPHONE SCREEN

Problem statement

You are given an integer array nums and an integer target. Find the two numbers in nums whose sum is target and return their indices.

The two numbers must come from different indices. The same value may appear at two indices, and those two indices can form the answer.
Exactly one pair of indices works.
Return the two zero-based indices as [i, j] with i < j.

Function

twoSum(nums: int[], target: int) → int[]

Examples

Example 1

nums = [4,9,1,6]target = 7return = [2,3]

Only 1 + 6 equals 7. Those numbers are at indices 2 and 3, so the answer is [2,3].

Example 2

nums = [5,1,5]target = 10return = [0,2]

The two 5s add up to 10. They are at indices 0 and 2. Equal numbers are fine as long as they come from different indices.

Example 3

nums = [-3,8,2,-1]target = -4return = [0,3]

-3 + (-1) = -4. These numbers are at indices 0 and 3, and the smaller index comes first.

Constraints

2 <= nums.length <= 1000
-10^6 <= nums[i] <= 10^6
-10^6 <= target <= 10^6
Exactly one pair of different indices i < j has nums[i] + nums[j] == target.