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Grokking the Coding Interview Patterns

Solution: Valid Triangle Number

Explore how to determine the number of valid triangles from an integer array by mastering the sort and search pattern. Understand the triangle inequality rule and apply two-pointer iteration techniques after sorting to efficiently count valid combinations. This lesson helps you implement a solution with O(n²) time complexity using controlled pointer movements.

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Statement

Given an array of integers, nums, determine the number of unique triplets that can be selected from the array such that the selected values can form the sides of a valid triangleA triangle is valid if the sum of the lengths of any two smaller sides is strictly greater than the length of the third largest side. For three sides a, b, c (such that a ≤ b ≤ c), the condition to form a valid triangle is a + b > c.. Return this count as the result.

Constraints:

  • 1<=1 <= nums.length <=1000<= 1000

  • 0<=0 <= nums[i] ...