为什么这种冒泡排序会以错误的顺序留下 2 个元素？

Question

I translated this code from a pseudo code example of the bubble sort algorithm, but when I implement it, it returns 2 values in the wrong place.

Here's the code:

 var numbers = [10, 9, 8, 7, 6, 5, 4, 3, 2, 1]; var swapMade; var temp; function setup() { swapMade = true; while (swapMade == true) { swapMade = false; for (var i = 0; i < numbers.length - 2; i++) { if (numbers[i] > numbers[i+1]) { temp = numbers[i]; numbers[i] = numbers[i+1]; numbers[i+1] = temp; swapMade = true; } } } console.log(JSON.stringify(numbers)); } setup();

This returns:

[2, 3, 4, 5, 6, 7, 8, 9, 10, 1]

So 10 and 1 are in the wrong place.

Does anyone know why?

Answer 1

You need to change i < numbers.length - 2 to i < numbers.length - 1 in your for-loop.

With i < numbers.length - 2 your loop will quit before evaluating the last element.

Answer 2

You should iterate until the index is equal to numbers.length - 1 . Currently, you are not comparing the second last element at index numbers.length - 2 with the last element since you stop right before numbers.length - 2 .

 var numbers = [10, 9, 8, 7, 6, 5, 4, 3, 2, 1]; var swapMade; var temp; function setup() { swapMade = true; while (swapMade) { swapMade = false; for (var i = 0; i < numbers.length - 1; i++) { if (numbers[i] > numbers[i+1]) { temp = numbers[i]; numbers[i] = numbers[i+1]; numbers[i+1] = temp; swapMade = true; } } } console.log(JSON.stringify(numbers)); } setup();

Answer 3

the code lacks one more iteration due to i < numbers.length -2

try changing that to i < numbers.length - 1 to fix it.

i < numbers.length - 1 will go from the first index (0) upto the second to the last index to account for the i+1