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

Fastest Merge of 2 Sorting array

function merge(a, b) {
  let i = 0,
    j = 0;
  let array = [];
  let counter = 0;
  while (i < a.length && j < b.length) {
    if (a[i] > b[j]) array[counter++] = b[j++];
    else if (a[i] < b[j]) array[counter++] = a[i++];
    else (array[counter++] = a[i++]), j++;
  }
  while (j < b.length) {
    array[counter++] = b[j++];
  }
  while (i < a.length) {
    array[counter++] = a[i++];
  }
  return array;
}
console.log(merge([1, 3], [2, 4, 5]));

console.log(merge([1, 3, 123, 125, 127], [2, 41, 50]));

Answer 2

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]));

Answer 3

can do with es6 spread operator

let a=[1,2,3,5,9]
let b=[4,6,7,8]

let newArray=[...a,...b].sort()
console.log(newArray)

Answer 4

// Everything fine but small mistake down there

function sortedArray(a,b){
    for(var i=0;i<b.length;i++){
        a.push(b[i]);
    }
    //console.log(a);
for(i=0;i<a.length;i++)
    {
        for(j=i+1;j<a.length;j++)
        {
            if(a[i]>a[j])
            {
                temp=a[i];
                a[i]=a[j];
                a[j]=temp;
            }
        }
    }
    
    //<!--You did a mistake here you have loop through for to get array elements-->
    for(i=0;i<a.length;i++){
    return a;
    }
}
console.log(sortedArray([1,2,3,5,9],[4,6,7,8]));

Answer 5

Merge two sorted arrays - Answer with comments

const mergeArrays = (arr1, arr2) => { // function to merge two sorted arrays
  if (!arr1 || !arr2) { // if only one array is passed
    return "Invalid Array" // message is returned
  }
  if (arr1.length < 1) { // if first array is empty
    if (arr2.length < 1) { // if second array is empty
      return "Both arrays are empty" // returns message
    }
    return arr2; // else returns second array
  }
  if (arr2.length < 1) { // if second array is empty
    if (arr1.length < 1) { // if both arrays are empty
      return "Both arrays are empty" // returns message
    }
    return arr1; // else returns first array
  }
  let small = []; // initializes empty array to store the smaller array
  let large = []; // initializes empty array to store the larger array
  arr1.length < arr2.length ? [small, large] = [arr1, arr2] : [small, large] = [arr2, arr1]; // stores smaller array in small and larger array in large
  const len1 = small.length; // stores length of small in len1
  const len2 = large.length; // stores length of large in len2
  let ansArr = []; // initializes an empty array to create the merged array
  let i = 0; // initializes i to 0 to iterate through small
  let j = 0; // initializes j to 0 to iterate through large
  while (small[i]!==undefined && large[j]!==undefined) { //while element in arrays at i and j position respectively exists
    if(small[i] < large[j]) { // if element from small is smaller than element in large
      ansArr.push(small[i]); // add that element to answer
      i++; // move to the next element
    } else { // if element from large is smaller than element in small
      ansArr.push(large[j]); // add that element to answer
      j++; // move to the next element
    }
  }
  if (i < len1) { // if i has not reached the end of array
    ansArr = [...ansArr, ...small.splice(i)]; // add the rest of the elements at the end of the answer
  } else { // if j has not reached the end of array
    ansArr = [...ansArr, ...large.splice(j)]; // add the rest of the elements at the end of the answer
  }
  return ansArr; // return answer
}

console.log(mergeArrays([0,1,5], [2,3,4,6,7,8,9])); // example

Answer 6

Shortest Merge Sorted arrays without sort() plus, without using third temp array.

function mergeSortedArray (a, b){
  let index = 0;

  while(b.length > 0 && a[index]) {
    if(a[index] > b[0]) {
      a.splice(index, 0, b.shift());
    }
    index++;
  }
  return [...a, ...b];
}
mergeSortedArray([1,2,3,5,9],[4,6,7,8])