Trying to remove all 0's from an array and return them in the same array
So for example if I have this as an array
let arrThree = [9,0,9,1,2,1,1,3,1,9,0,0,9,0,0,0,0,0,0,0]
I would get this:
let arrThree = [9,9,9,1,2,1,1,3,1,9,9,0,0,0,0,0,0,0,0,0,0,0]
This is what I wrote:
var remove = function (arr) {
let test = [];
for(let i = 0; i < arr.length; i++){
arr[i] === 0 ? test.push(arr.splice(i,1)) : false //if i is 0 then we want to push that into another array
}
arr.push(...test)
return [].concat(...arr)
}
When I run this function I get this
[
9, 9, 1, 2, 1, 1, 3,
1, 9, 0, 9, 0, 0, 0,
0, 0, 0, 0, 0, 0
]
Not sure where I am going wrong?
The issue with your code is you change the length of arr with arr.splice(i,1). This messes up the loop condition i < arr.length.
To fix your code, you can loop backwards through the array. So as the length of the array shortens, i is still valid.
let arrThree = [9,0,9,1,2,1,1,3,1,9,0,0,9,0,0,0,0,0,0,0];
var remove = function(arr) {
let test = [];
for(let i = arr.length - 1; i >= 0; --i) {
if (arr[i] === 0) test.push(arr.splice(i, 1)[0]);
}
return arr.concat(test);
}
console.log(remove(arrThree));There are a few other ways to do this. One is to use filter to create 2 arrays - one with no 0 and one with all 0 and join them:
let arrThree = [9,0,9,1,2,1,1,3,1,9,0,0,9,0,0,0,0,0,0,0];
let remove = (arr) => arr.filter(i => i != 0).concat(arr.filter(i => i == 0));
console.log(remove(arrThree));You need only two iterations, one for finding non zero values and another to put zeroes to the right side until end of the array. You need no array pushing or splicing.
const
move0 = array => {
let i = 0,
j = 0;
while (i < array.length) {
if (array[i]) array[j++] = array[i];
i++;
}
while (j < array.length) {
array[j] = '#'; // in reality it is zero
j++;
}
},
array = [9, 0, 9, 1, 2, 1, 1, 3, 1, 9, 0, 0, 9, 0, 0, 0, 0, 0, 0, 0];
move0(array)
console.log(...array);If you don't need to have any sorting on the non-zero elements, a rather efficient solution would be to swap the left-most 0 with the right-most non-zero element. Once your indices for tracking where you are on the left and right cross you'll know you're done.
function moveZeros(arr) {
let i = 0;
let j = arr.length - 1;
while(i < j) {
// Found a 0 to the left of a non-zero, swap.
if(arr[i] == 0 && arr[j] != 0) {
let tmp = arr[j];
arr[j] = arr[i];
arr[i] = tmp;
}
// Find a zero
if(arr[i] != 0) {
i++;
}
// Find a non-zero
if(arr[j] == 0) {
j--;
}
}
return arr;
}
console.log(moveZeros([1,2,0,3,0,0,0]));
console.log(moveZeros([9,0,9,1,2,1,1,3,1,9,0,0,9,0,0,0,0,0,0,0]));