CODEWITHSUNDEEP
javascriptsortingbubble-sort
user12126167
user12126167

Reputation:

Why does this bubble sort leave 2 elements in the wrong order?

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?

Upvotes: 0

Views: 105

Answers (3)

mmfallacy
mmfallacy

Reputation: 186

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

Upvotes: 0

Unmitigated
Unmitigated

Reputation: 89364

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();

Upvotes: 1

zeterain
zeterain

Reputation: 1140

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.

Upvotes: 1

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