FastPrep
Problem · Array

Count Good Tuples

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Problem statement

You are given an integer array a. Consider every tuple of three consecutive elements.

A tuple is good if exactly two of its three values are equal. For example, (2, 1, 2) is a good tuple, while (1, 1, 1) and (1, 2, 3) are not.

Return the number of good tuples in a. Tuples may overlap.

A solution with time complexity no worse than O(a.length^2) fits within the execution time limit.

Function

solution(a: int[]) → int

Examples

Example 1

a = [1, 1, 1, 2, 1, 3, 4]return = 2

The five consecutive tuples are:

  • (1, 1, 1): all three values are equal, so this is not a good tuple.
  • (1, 1, 2): exactly two values are equal, so this is a good tuple.
  • (1, 2, 1): exactly two values are equal, so this is a good tuple.
  • (2, 1, 3): all three values are distinct, so this is not a good tuple.
  • (1, 3, 4): all three values are distinct, so this is not a good tuple.

Exactly two tuples are good, so the answer is 2.

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public int solution(int[] a) {
  // Write your code here.
}
a[1, 1, 1, 2, 1, 3, 4]
expected2
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