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1. Two Sum

easyAsked at Wix

Find two indices in an array whose values sum to a target; classic hash-map warm-up at Wix.

By Alex Chen, Founder, InterviewChamp.AI · Last verified

Problem

Given an array of integers nums and an integer target, return indices of the two numbers such that they add up to target. You may assume that each input would have exactly one solution.

Constraints

  • 2 <= nums.length <= 10^4
  • -10^9 <= nums[i], target <= 10^9

Examples

Example 1

Input
nums=[2,7,11,15], target=9
Output
[0,1]

Example 2

Input
nums=[3,2,4], target=6
Output
[1,2]

Approaches

1. Brute force

Nested loops check every pair.

Time
O(n^2)
Space
O(1)
for (let i=0;i<n;i++) for (let j=i+1;j<n;j++) if (nums[i]+nums[j]===target) return [i,j];

Tradeoff:

2. Hash map

One pass storing complements gives O(n).

Time
O(n)
Space
O(n)
function twoSum(nums, target) {
  const seen = new Map();
  for (let i = 0; i < nums.length; i++) {
    const c = target - nums[i];
    if (seen.has(c)) return [seen.get(c), i];
    seen.set(nums[i], i);
  }
}

Tradeoff:

Wix-specific tips

Wix interviewers expect clean ES6 JavaScript with Map over plain objects and a quick mention of how the same lookup pattern powers their site-builder's component-id resolution.

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Output

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