g0901_1000.s0923_3sum_with_multiplicity

Class Solution

java.lang.Object

g0901_1000.s0923_3sum_with_multiplicity.Solution

public class Solution
extends Object

923 - 3Sum With Multiplicity.

Medium

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.

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

Example 1:

Input: arr = [1,1,2,2,3,3,4,4,5,5], target = 8

Output: 20

Explanation:

Enumerating by the values (arr[i], arr[j], arr[k]): 
(1, 2, 5) occurs 8 times; 
(1, 3, 4) occurs 8 times; 
(2, 2, 4) occurs 2 times; 
(2, 3, 3) occurs 2 times.

Example 2:

Input: arr = [1,1,2,2,2,2], target = 5

Output: 12

Explanation:

arr[i] = 1, arr[j] = arr[k] = 2 occurs 12 times:

We choose one 1 from [1,1] in 2 ways,

and two 2s from [2,2,2,2] in 6 ways.

Constraints:

• 3 <= arr.length <= 3000
• 0 <= arr[i] <= 100
• 0 <= target <= 300

Constructor Summary

Constructors

Constructor and Description
Solution()

Method Summary

Modifier and Type	Method and Description
int	threeSumMulti(int[] arr, int target)

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

Solution

public Solution()

Method Detail

threeSumMulti

public int threeSumMulti(int[] arr,
                         int target)