{ "data": { "question": { "questionId": "959", "questionFrontendId": "923", "boundTopicId": null, "title": "3Sum With Multiplicity", "titleSlug": "3sum-with-multiplicity", "content": "

Given an integer array arr, and an integer target, return the number of tuples i, j, k such that i < j < k and arr[i] + arr[j] + arr[k] == target.

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As the answer can be very large, return it modulo 109 + 7.

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Example 1:

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\nInput: arr = [1,1,2,2,3,3,4,4,5,5], target = 8\nOutput: 20\nExplanation: \nEnumerating by the values (arr[i], arr[j], arr[k]):\n(1, 2, 5) occurs 8 times;\n(1, 3, 4) occurs 8 times;\n(2, 2, 4) occurs 2 times;\n(2, 3, 3) occurs 2 times.\n
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Example 2:

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\nInput: arr = [1,1,2,2,2,2], target = 5\nOutput: 12\nExplanation: \narr[i] = 1, arr[j] = arr[k] = 2 occurs 12 times:\nWe choose one 1 from [1,1] in 2 ways,\nand two 2s from [2,2,2,2] in 6 ways.\n
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Example 3:

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\nInput: arr = [2,1,3], target = 6\nOutput: 1\nExplanation: (1, 2, 3) occured one time in the array so we return 1.\n
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Constraints:

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Most standard library headers are already included automatically for your convenience.

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OpenJDK 17. Java 8 features such as lambda expressions and stream API can be used.

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Python 2.7.12.

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C# 10 with .NET 6 runtime

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Node.js 16.13.2.

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Python 3.10.

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Scala 2.13.7.

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Kotlin 1.9.0.

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