how to merge two sorted array in one sorted array in JavaScript without using sort()

Question

In this program merged two array and then sorted using temp.but this not correct method.because two array are sorted ,so method should be unique i.e. merging of two sorted i

Answer 1

Merging two sorted arrays.

function merge(a, b) {
  let i = a.length - 1;
  let j = b.length - 1;
  let k = i + j + 1; //(a.length + b.length - 1) == (i + j + 2 - 1) == (i + j + 1)

  while (k >= 0) {
    if (a[i] > b[j] || j < 0) {
      a[k] = a[i];
      i--;
    } else {
      a[k] = b[j];
      j--;
    }
    k--;
  }
  return a;
}

console.log(merge([1, 3, 5, 7, 9, 11, 13, 15, 17, 19, 21], [2, 4, 6, 8, 10, 12, 14, 16, 18, 20]));

More compact code:

function merge(a, b) {
  let i = a.length - 1;
  let j = b.length - 1;
  let k = i + j + 1; //(a.length + b.length - 1) == (i + j + 2 - 1) == (i + j + 1)

  while (k >= 0) {
    a[k--] = (a[i] > b[j] || j < 0) ? a[i--] : b[j--];
  }
  return a;
}

console.log(merge([1, 3, 5, 7, 9, 11, 13, 15, 17, 19, 21], [2, 4, 6, 8, 10, 12, 14, 16, 18, 20]));