插入排序不适用于JavaScript

Question

I don't know why my script doesn't work it returns the same length as my input but the algorythm, seem to don't work.

 var n = prompt("Entrer la taille de votre tableau:"); a = new Array(); b = new Array(); a.length = n; b.length = n; var i = 0, j = 0; for (i = 0; i < n; i++) { a[i] = prompt("Entrer les valeurs de votre tableau:"); }; console.log(a); // Algorithm part : for (i = 0; i < n; i++) { b[j] = a[i]; for (j = i; j > 0 && a[j - 1] > b[i]; j--) { a[j] = a[j - 1]; } a[j] = b[i]; } console.log(b); console.log(b.length); 

Answer 1

I'm not really sure how you envisioned that code working. You're using i in places where you should be using j and assigning values back and forth between arrays a and b in a way that doesn't make sense to me.

The way to make this work is to only work within the b array, and just copy values in from a one at a time. In the inner loop, j should be initialized to the value of i , but i shouldn't be used in that loop after that.

One more problem was that you weren't converting the inputs to numbers, so all of the comparisons were being made as string comparisons.

The following should work:

 var n = prompt("Entrer la taille de votre tableau:"); a = new Array(); b = new Array(); a.length = n; b.length = n; var i = 0; var j = 0; var temp; for (i = 0; i < n; i++) { a[i] = Number(prompt("Entrer les valeurs de votre tableau:")); }; console.log(a); // Algorithm part : for (i = 0; i < n; i++) { // Place the ith value of a in b b[i] = a[i]; // Move backwards from i, swapping values until the inserted value is in the correct place for (j = i; j > 0 && b[j - 1] > b[j]; j--) { // swap temp = b[j]; b[j] = b[j - 1]; b[j - 1] = temp; } } console.log(b); console.log(b.length); 

Answer 2

j is not defined at the start of the loop, so the line 'b[j]=a[i]' does not do what you might expect. You are also sorting in a not in b . I don't think that is what you intended so the following code sorts in b.

//define some values
const a=[3,6,8,4,5,2,7,1];
const n=a.length;
const b=new Array(n);

//now do the insertion sort
for (let i = 0; i < n; i++) {
  let j;
  for (j = i; j > 0 && b[j - 1] > a[i]; j--) {
    b[j] = b[j - 1];
  }
  b[j] = a[i];
}

console.log(b);