#01EasyFoundations · 71% acceptance

Two-Pointer Sum

ArrayTwo PointersHash Map

You are handed an array of integer measurements `nums` and a target value `target`.

Return the indices of the two measurements that add up to `target`. You may assume exactly one valid answer exists, and you cannot use the same reading twice.

If you have ever scanned a gel for two bands that sum to a known weight, you already understand the shape of this problem — we are just making it formal.

Examples

Input: nums = [2, 7, 11, 15], target = 9

Output: [0, 1]

Note: nums[0] + nums[1] = 2 + 7 = 9.

Input: nums = [3, 2, 4], target = 6

Output: [1, 2]

Constraints

·2 ≤ nums.length ≤ 10^4
·-10^9 ≤ nums[i] ≤ 10^9
·Exactly one valid pair exists.

Hints

solution.pyPython 3

def two_sum(nums, target):
    seen = {}
    for i, n in enumerate(nums):
        # complement we need to find
        need = target - n
        if need in seen:
            return [seen[need], i]
        seen[n] = i
    return []

Test console

// hit Run to execute the sample tests

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