javaScript solution to Codility PermMissingElem problem (Easy)

Codility: PermMissingElem

// ANSWER:
function solution(A) {
    // make a dictionary of expected values: O(n)
    let map = []
   
    for (let i = 0; i < A.length + 1; i+= 1) {
        map[i] = { num: i+1, bool: -1 }
    }
    
    // evaluate subset against dictionary, marking included values: O(n)
    for (let j = 0; j < A.length; j+= 1) {
        let num = A[j] // find the num in A
        map[num -1].bool = 0 // mark as found in map
    }
    
    // evaluate dicionary for the missing values: O(n)
    for (let k = 0; k < map.length; k+= 1) {
        if(map[k].bool === - 1) {
            return map[k].num
        }
    }
}

// QUESTION:  https://app.codility.com/demo/results/training64HF3R-BX7/

function solution(A) {
  if (!A.length) return 1;
  A = A.sort((a, b) => a - b);
  for (let i = 0; i < A.length + 1; i++) {
    if (A[i] !== i + 1) {
      return i + 1;
    }
  }
}

A small improvement to what @yamankatby wrote is to use Unit32Array, in order to sort faster:

function solution(A) { if (!A.length) return 1; A = new Uint32Array(A).sort(); for (let i=0; i<A.length + 1; i++){ if (A[i] !== i+1) return i+1; } }