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AVAILABLE LESSONS:

Lesson 1

Iterations

Lesson 2

Arrays

Lesson 3

Time Complexity

Lesson 4

Counting Elements

Lesson 5

Prefix Sums

Lesson 6

Sorting

Lesson 7

Stacks and Queues

Lesson 8

Leader

Lesson 9

Maximum slice problem

Lesson 10

Prime and composite numbers

Lesson 11

Sieve of Eratosthenes

Lesson 12

Euclidean algorithm

Lesson 13

Fibonacci numbers

Lesson 14

Binary search algorithm

Lesson 15

Caterpillar method

Lesson 16

Greedy algorithms

Lesson 17

Dynamic programming

Lesson 99

Future training

Count the number of triangles that can be built from a given set of edges.

Spoken language:

An array A consisting of N integers is given. A triplet (P, Q, R) is *triangular* if it is possible to build a triangle with sides of lengths A[P], A[Q] and A[R]. In other words, triplet (P, Q, R) is triangular if 0 ≤ P < Q < R < N and:

- A[P] + A[Q] > A[R],
- A[Q] + A[R] > A[P],
- A[R] + A[P] > A[Q].

For example, consider array A such that:

There are four triangular triplets that can be constructed from elements of this array, namely (0, 2, 4), (0, 2, 5), (0, 4, 5), and (2, 4, 5).

Write a function:

int solution(int A[], int N);

that, given an array A consisting of N integers, returns the number of triangular triplets in this array.

For example, given array A such that:

the function should return 4, as explained above.

Write an ** efficient** algorithm for the following assumptions:

- N is an integer within the range [0..1,000];
- each element of array A is an integer within the range [1..1,000,000,000].

Copyright 2009–2023 by Codility Limited. All Rights Reserved. Unauthorized copying, publication or disclosure prohibited.

An array A consisting of N integers is given. A triplet (P, Q, R) is *triangular* if it is possible to build a triangle with sides of lengths A[P], A[Q] and A[R]. In other words, triplet (P, Q, R) is triangular if 0 ≤ P < Q < R < N and:

- A[P] + A[Q] > A[R],
- A[Q] + A[R] > A[P],
- A[R] + A[P] > A[Q].

For example, consider array A such that:

There are four triangular triplets that can be constructed from elements of this array, namely (0, 2, 4), (0, 2, 5), (0, 4, 5), and (2, 4, 5).

Write a function:

int solution(vector<int> &A);

that, given an array A consisting of N integers, returns the number of triangular triplets in this array.

For example, given array A such that:

the function should return 4, as explained above.

Write an ** efficient** algorithm for the following assumptions:

- N is an integer within the range [0..1,000];
- each element of array A is an integer within the range [1..1,000,000,000].

Copyright 2009–2023 by Codility Limited. All Rights Reserved. Unauthorized copying, publication or disclosure prohibited.

An array A consisting of N integers is given. A triplet (P, Q, R) is *triangular* if it is possible to build a triangle with sides of lengths A[P], A[Q] and A[R]. In other words, triplet (P, Q, R) is triangular if 0 ≤ P < Q < R < N and:

- A[P] + A[Q] > A[R],
- A[Q] + A[R] > A[P],
- A[R] + A[P] > A[Q].

For example, consider array A such that:

There are four triangular triplets that can be constructed from elements of this array, namely (0, 2, 4), (0, 2, 5), (0, 4, 5), and (2, 4, 5).

Write a function:

int solution(vector<int> &A);

that, given an array A consisting of N integers, returns the number of triangular triplets in this array.

For example, given array A such that:

the function should return 4, as explained above.

Write an ** efficient** algorithm for the following assumptions:

- N is an integer within the range [0..1,000];
- each element of array A is an integer within the range [1..1,000,000,000].

Copyright 2009–2023 by Codility Limited. All Rights Reserved. Unauthorized copying, publication or disclosure prohibited.

*triangular* if it is possible to build a triangle with sides of lengths A[P], A[Q] and A[R]. In other words, triplet (P, Q, R) is triangular if 0 ≤ P < Q < R < N and:

- A[P] + A[Q] > A[R],
- A[Q] + A[R] > A[P],
- A[R] + A[P] > A[Q].

For example, consider array A such that:

Write a function:

class Solution { public int solution(int[] A); }

For example, given array A such that:

the function should return 4, as explained above.

Write an ** efficient** algorithm for the following assumptions:

- N is an integer within the range [0..1,000];
- each element of array A is an integer within the range [1..1,000,000,000].

*triangular* if it is possible to build a triangle with sides of lengths A[P], A[Q] and A[R]. In other words, triplet (P, Q, R) is triangular if 0 ≤ P < Q < R < N and:

- A[P] + A[Q] > A[R],
- A[Q] + A[R] > A[P],
- A[R] + A[P] > A[Q].

For example, consider array A such that:

Write a function:

int solution(List<int> A);

For example, given array A such that:

the function should return 4, as explained above.

Write an ** efficient** algorithm for the following assumptions:

- N is an integer within the range [0..1,000];
- each element of array A is an integer within the range [1..1,000,000,000].

*triangular* if it is possible to build a triangle with sides of lengths A[P], A[Q] and A[R]. In other words, triplet (P, Q, R) is triangular if 0 ≤ P < Q < R < N and:

- A[P] + A[Q] > A[R],
- A[Q] + A[R] > A[P],
- A[R] + A[P] > A[Q].

For example, consider array A such that:

Write a function:

func Solution(A []int) int

For example, given array A such that:

the function should return 4, as explained above.

Write an ** efficient** algorithm for the following assumptions:

- N is an integer within the range [0..1,000];
- each element of array A is an integer within the range [1..1,000,000,000].

*triangular* if it is possible to build a triangle with sides of lengths A[P], A[Q] and A[R]. In other words, triplet (P, Q, R) is triangular if 0 ≤ P < Q < R < N and:

- A[P] + A[Q] > A[R],
- A[Q] + A[R] > A[P],
- A[R] + A[P] > A[Q].

For example, consider array A such that:

Write a function:

class Solution { public int solution(int[] A); }

For example, given array A such that:

the function should return 4, as explained above.

Write an ** efficient** algorithm for the following assumptions:

- N is an integer within the range [0..1,000];
- each element of array A is an integer within the range [1..1,000,000,000].

*triangular* if it is possible to build a triangle with sides of lengths A[P], A[Q] and A[R]. In other words, triplet (P, Q, R) is triangular if 0 ≤ P < Q < R < N and:

- A[P] + A[Q] > A[R],
- A[Q] + A[R] > A[P],
- A[R] + A[P] > A[Q].

For example, consider array A such that:

Write a function:

class Solution { public int solution(int[] A); }

For example, given array A such that:

the function should return 4, as explained above.

Write an ** efficient** algorithm for the following assumptions:

- N is an integer within the range [0..1,000];
- each element of array A is an integer within the range [1..1,000,000,000].

*triangular* if it is possible to build a triangle with sides of lengths A[P], A[Q] and A[R]. In other words, triplet (P, Q, R) is triangular if 0 ≤ P < Q < R < N and:

- A[P] + A[Q] > A[R],
- A[Q] + A[R] > A[P],
- A[R] + A[P] > A[Q].

For example, consider array A such that:

Write a function:

function solution(A);

For example, given array A such that:

the function should return 4, as explained above.

Write an ** efficient** algorithm for the following assumptions:

- N is an integer within the range [0..1,000];
- each element of array A is an integer within the range [1..1,000,000,000].

*triangular* if it is possible to build a triangle with sides of lengths A[P], A[Q] and A[R]. In other words, triplet (P, Q, R) is triangular if 0 ≤ P < Q < R < N and:

- A[P] + A[Q] > A[R],
- A[Q] + A[R] > A[P],
- A[R] + A[P] > A[Q].

For example, consider array A such that:

Write a function:

fun solution(A: IntArray): Int

For example, given array A such that:

the function should return 4, as explained above.

Write an ** efficient** algorithm for the following assumptions:

- N is an integer within the range [0..1,000];
- each element of array A is an integer within the range [1..1,000,000,000].

*triangular* if it is possible to build a triangle with sides of lengths A[P], A[Q] and A[R]. In other words, triplet (P, Q, R) is triangular if 0 ≤ P < Q < R < N and:

- A[P] + A[Q] > A[R],
- A[Q] + A[R] > A[P],
- A[R] + A[P] > A[Q].

For example, consider array A such that:

Write a function:

function solution(A)

For example, given array A such that:

the function should return 4, as explained above.

Write an ** efficient** algorithm for the following assumptions:

- N is an integer within the range [0..1,000];
- each element of array A is an integer within the range [1..1,000,000,000].

Note: All arrays in this task are zero-indexed, unlike the common Lua convention. You can use `#A` to get the length of the array A.

*triangular* if it is possible to build a triangle with sides of lengths A[P], A[Q] and A[R]. In other words, triplet (P, Q, R) is triangular if 0 ≤ P < Q < R < N and:

- A[P] + A[Q] > A[R],
- A[Q] + A[R] > A[P],
- A[R] + A[P] > A[Q].

For example, consider array A such that:

Write a function:

int solution(NSMutableArray *A);

For example, given array A such that:

the function should return 4, as explained above.

Write an ** efficient** algorithm for the following assumptions:

- N is an integer within the range [0..1,000];
- each element of array A is an integer within the range [1..1,000,000,000].

*triangular* if it is possible to build a triangle with sides of lengths A[P], A[Q] and A[R]. In other words, triplet (P, Q, R) is triangular if 0 ≤ P < Q < R < N and:

- A[P] + A[Q] > A[R],
- A[Q] + A[R] > A[P],
- A[R] + A[P] > A[Q].

For example, consider array A such that:

Write a function:

function solution(A: array of longint; N: longint): longint;

For example, given array A such that:

the function should return 4, as explained above.

Write an ** efficient** algorithm for the following assumptions:

- N is an integer within the range [0..1,000];
- each element of array A is an integer within the range [1..1,000,000,000].

*triangular* if it is possible to build a triangle with sides of lengths A[P], A[Q] and A[R]. In other words, triplet (P, Q, R) is triangular if 0 ≤ P < Q < R < N and:

- A[P] + A[Q] > A[R],
- A[Q] + A[R] > A[P],
- A[R] + A[P] > A[Q].

For example, consider array A such that:

Write a function:

function solution($A);

For example, given array A such that:

the function should return 4, as explained above.

Write an ** efficient** algorithm for the following assumptions:

- N is an integer within the range [0..1,000];
- each element of array A is an integer within the range [1..1,000,000,000].

*triangular* if it is possible to build a triangle with sides of lengths A[P], A[Q] and A[R]. In other words, triplet (P, Q, R) is triangular if 0 ≤ P < Q < R < N and:

- A[P] + A[Q] > A[R],
- A[Q] + A[R] > A[P],
- A[R] + A[P] > A[Q].

For example, consider array A such that:

Write a function:

sub solution { my (@A) = @_; ... }

For example, given array A such that:

the function should return 4, as explained above.

Write an ** efficient** algorithm for the following assumptions:

- N is an integer within the range [0..1,000];
- each element of array A is an integer within the range [1..1,000,000,000].

*triangular* if it is possible to build a triangle with sides of lengths A[P], A[Q] and A[R]. In other words, triplet (P, Q, R) is triangular if 0 ≤ P < Q < R < N and:

- A[P] + A[Q] > A[R],
- A[Q] + A[R] > A[P],
- A[R] + A[P] > A[Q].

For example, consider array A such that:

Write a function:

def solution(A)

For example, given array A such that:

the function should return 4, as explained above.

Write an ** efficient** algorithm for the following assumptions:

- N is an integer within the range [0..1,000];
- each element of array A is an integer within the range [1..1,000,000,000].

*triangular* if it is possible to build a triangle with sides of lengths A[P], A[Q] and A[R]. In other words, triplet (P, Q, R) is triangular if 0 ≤ P < Q < R < N and:

- A[P] + A[Q] > A[R],
- A[Q] + A[R] > A[P],
- A[R] + A[P] > A[Q].

For example, consider array A such that:

Write a function:

def solution(a)

For example, given array A such that:

the function should return 4, as explained above.

Write an ** efficient** algorithm for the following assumptions:

- N is an integer within the range [0..1,000];
- each element of array A is an integer within the range [1..1,000,000,000].

*triangular* if it is possible to build a triangle with sides of lengths A[P], A[Q] and A[R]. In other words, triplet (P, Q, R) is triangular if 0 ≤ P < Q < R < N and:

- A[P] + A[Q] > A[R],
- A[Q] + A[R] > A[P],
- A[R] + A[P] > A[Q].

For example, consider array A such that:

Write a function:

object Solution { def solution(a: Array[Int]): Int }

For example, given array A such that:

the function should return 4, as explained above.

Write an ** efficient** algorithm for the following assumptions:

- N is an integer within the range [0..1,000];
- each element of array A is an integer within the range [1..1,000,000,000].

*triangular* if it is possible to build a triangle with sides of lengths A[P], A[Q] and A[R]. In other words, triplet (P, Q, R) is triangular if 0 ≤ P < Q < R < N and:

- A[P] + A[Q] > A[R],
- A[Q] + A[R] > A[P],
- A[R] + A[P] > A[Q].

For example, consider array A such that:

Write a function:

public func solution(_ A : inout [Int]) -> Int

For example, given array A such that:

the function should return 4, as explained above.

Write an ** efficient** algorithm for the following assumptions:

- N is an integer within the range [0..1,000];
- each element of array A is an integer within the range [1..1,000,000,000].

*triangular* if it is possible to build a triangle with sides of lengths A[P], A[Q] and A[R]. In other words, triplet (P, Q, R) is triangular if 0 ≤ P < Q < R < N and:

- A[P] + A[Q] > A[R],
- A[Q] + A[R] > A[P],
- A[R] + A[P] > A[Q].

For example, consider array A such that:

Write a function:

function solution(A: number[]): number;

For example, given array A such that:

the function should return 4, as explained above.

Write an ** efficient** algorithm for the following assumptions:

- N is an integer within the range [0..1,000];
- each element of array A is an integer within the range [1..1,000,000,000].

*triangular* if it is possible to build a triangle with sides of lengths A[P], A[Q] and A[R]. In other words, triplet (P, Q, R) is triangular if 0 ≤ P < Q < R < N and:

- A[P] + A[Q] > A[R],
- A[Q] + A[R] > A[P],
- A[R] + A[P] > A[Q].

For example, consider array A such that:

Write a function:

Private Function solution(A As Integer()) As Integer

For example, given array A such that:

the function should return 4, as explained above.

Write an ** efficient** algorithm for the following assumptions:

- N is an integer within the range [0..1,000];
- each element of array A is an integer within the range [1..1,000,000,000].