JSFiddle - React, Tailwind, and code Playground

by floor_

JavaScript

function solution(A, K) {
  var n = A.length;
  for (var i = 0; i < n - 1; i++) {
    var inSequence = A[i] != 1 || A[i] == k;
    if (A[i] > A[i+1] || (A[i] == A[i+1] && inSequence))
    	return false;
  }
  if (A[0] != 1 || A[n - 1] != K)
    return false;
  else
    return true;
}

console.log(solution([1, 2, 3, 2], 2)); //false
console.log(solution([1, 2], 1)); //false
console.log(solution([1, 0, 1], 1)); //false
console.log(solution([1, 1, 2, 3, 3], 3)); //true
console.log(solution([1, 2, 3, 4, 5], 5)); //true
console.log(solution([1, 2, 3, 5, 5], 5)); //false
console.log(solution([1, 2, 3, 3], 3)); //true


// [1,0,1], 1