Determine whether a triangle can be built from a given set of edges.

Task description: Determine whether a triangle can be built from a given set of edges

An array A consisting of N integers is given. A 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: A[0] = 10 A[1] = 2 A[2] = 5 A[3] = 1 A[4] = 8 A[5] = 20

Triplet (0, 2, 4) is triangular.

Write a function:

function solution(A);

that, given an array A consisting of N integers, returns 1 if there exists a triangular triplet for this array and returns 0 otherwise.

For example, given array A such that: A[0] = 10 A[1] = 2 A[2] = 5 A[3] = 1 A[4] = 8 A[5] = 20

the function should return 1, as explained above. Given array A such that: A[0] = 10 A[1] = 50 A[2] = 5 A[3] = 1

the function should return 0.

Write an efficient algorithm for the following assumptions:

  • N is an integer within the range [0..100,000];
  • each element of array A is an integer within the range [−2,147,483,648..2,147,483,647].
function solution(A) {
    // write your code in JavaScript (Node.js 4.0.0)
    
    if(A.length < 3) {
        return 0;
    }
    
    A.sort(function(a, b) {
        return a-b;
    });
    
    for(var i=2; i<A.length; i++) {
        if(validate(A[i-2], A[i-1], A[i])) {
            return 1;
        }
    }
    
    return 0;
}

function validate(val0, val1, val2) {
    var result = true;
    
    result = result && (val0 + val1 > val2);
    result = result && (val0 + val2 > val1);
    result = result && (val1 + val2 > val0);
    
    return result;
}

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