- A+

I'm trying to write an insertion sort method, and I have managed to finish it, but I don't understand why my first version cannot work correctly.

Here's my first attempt:

`public static void insertionSort(int[] list) { for (int i = 1; i < list.length; i++) { int current = list[i]; for (int k = i - 1; k >= 0 && current < list[k]; k--) { list[i] = list[k]; list[k] = current; } } } public static void main(String[] args) { int[] list = {8, 22, 90, 10}; insertionSort(list); } `

My output for the above code is: 8, 10, 10, 22

But the answer would be correct if the inside for-loop, at line 5, is changed from: `list[i] = list[k];`

to: `list[k + 1] = list[k];`

To my understanding, `k + 1`

is equal to `i`

, but it must be different in loop counting and I can't figure out how. I have tried many sets of input, and only values that lie between the range of the 2 first indexes (in this case 8 and 22) would be incorrect.

`k + 1`

*is* equal to `i`

, but only in the first iteration of the inner for loop. `int k = i - 1`

is only run once per iteration of the *outer* for loop.

In the second iteration of the inner for loop, `k`

is decremented but `i`

is not. Therefore, `k + 1`

and `i`

are not interchangeable inside the inner for loop.

`// second iteration of the outer for loop, second iteration of the inner for loop: list[i] = list[k]; // means "list[2] = list[0] // whereas list[k + 1] = list[k]; // means "list[1] = list[0]" `