I've got these two arrays and I need to obtain c. I managed to obtain a solution with two fors and conditionals, but I'm sure something better than O^2 can be obtained with JS.
a = [3, 2, 1, 3]
b = ['a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i']
c = [['a', 'b', 'c'], ['d', 'e'], ['f'], ['g', 'h', 'i']]
For fun purpose I wrote it in a coincisive way, hope you like it:
const a = [3, 2, 1, 3];
const b = ["a", "b", "c", "d", "e", "f", "g", "h", "i"];
const bClone = [...b];
const array = a.map((num, index) =>
Array.from({ length: num }, () => bClone.shift())
);
console.log(array);Of course controls should be added, thanks
b, even though b is supposed to be a constant.
I don't have that much good background in algorithms but I think this is better than two fors:
let a = [3, 2, 1, 3]
,b = ['a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i']
let head = 0
let result = a.map((e) => {
let subArr = b.slice(head,head+e)
head +=e
return subArr
})
console.log(result)
One possibility is to combine map with splice, taking care not to mutate the original array:
const a = [3, 2, 1, 3];
const b = ['a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i'];
function slices(sizes, arr){
const clonedArr = [].concat(arr); // clone array to prevent mutation
return sizes.map(size => clonedArr.splice(0,size));
}
console.log(slices(a,b)); // [['a', 'b', 'c'], ['d', 'e'], ['f'], ['g', 'h', 'i']]
Alternatively, avoiding mutation altogether, you could use slice with a slightly convoluted reduce:
const slicesByReduce = (sizes, arr) => sizes
.reduce(({start, acc}, size) => ({
start: start + size,
acc: [...acc, arr.slice(start, start + size)]
}),{
start: 0,
acc: []
}).acc;
console.log(slicesByReduce(a,b)); // [['a', 'b', 'c'], ['d', 'e'], ['f'], ['g', 'h', 'i']]
slice?Iterate your array of "sizes" and get slices of the second array into the result, like this:
const a = [3, 2, 1, 3]
const b = ['a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i']
const c = [];
var index = 0;
for (var size of a) {
c.push(b.slice(index, index + size));
index += size;
}
console.log(c)
//c = [['a', 'b', 'c'], ['d', 'e'], ['f'], ['g', 'h', 'i']]Also, if you are going to work with arrays in JavaScript, please look into:
