Counting Triangles

You are given an array of N non-negative integers, A0, A1 ,…, AN-1.
Considering each array element Ai as the edge length of some line segment, count the number of triangles which you can form using these array values.


  1. You can use any value only once while forming each triangle. Order of choosing the edge lengths doesn’t matter. Any triangle formed should have a positive area.

  2. Return answer modulo 109 + 7.

For example,

A = [1, 1, 1, 2, 2]

Return: 4
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