We are required to declare a function, let’s say insertAllPositions, which takes two arguments −
an element, x, and an array, arr. Functions must return an array of arrays, with each array corresponding to arr with x inserted in a possible position.
That is, if arr is the length N, then the result is an array with N + 1 arrays −
For example, the result of insertAllPositions(10, [1,2,3]) should be −
const output = [ [10,1,2,3], [1,10,2,3], [1,2,10,3], [1,2,3,10] ];
We are required to write this function purely using recursion.
Example
Following is the code −
const arr = [1, 2, 3]; const num = 10; const insertAllPositions = (num, arr) => { return arr.length ? [[num, ...arr]] .concat(insertAllPositions(num, arr.slice(1)) .map(el => { return [arr[0]].concat(el); })) : [[num]] }; console.log(insertAllPositions(num, arr));
Output
This will produce the following output on console −
[ [ 10, 1, 2, 3 ], [ 1, 10, 2, 3 ], [ 1, 2, 10, 3 ], [ 1, 2, 3, 10 ] ]