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4Sum Index Quadruples

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Problem statement

Given an integer array nums and an integer target, return every index quadruple [i, j, k, l] such that i < j < k < l and nums[i] + nums[j] + nums[k] + nums[l] == target.

Indices, not values, define a result. Distinct index combinations must therefore be retained even when their values are equal. Do not reorder or mutate nums. Return the quadruples in lexicographic order.

Function

fourSumIndices(nums: int[], target: long) → int[][]

Examples

Example 1

nums = [1,0,-1,0,-2,2]target = 0return = [[0,1,2,3],[0,2,4,5],[1,3,4,5]]

Each listed increasing index tuple selects four values whose sum is zero. No other index tuple qualifies.

Example 2

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

All five ways to choose four different indices are retained even though every selected value is identical.

Constraints

0 <= nums.length <= 400.
-10^9 <= nums[i], target <= 10^9.
The number of returned quadruples is at most 100000.
Use 64-bit arithmetic for intermediate sums.