The sorting method does not work correctly.

Question

Hello.

Tell me, please, why the sorting method does not work correctly, the figure 5 disappears somewhere. Everything works in the Pascal language (the code translated with maximum accuracy).

 class test { protected static int a, b; protected static int[] array = { 2, 21, 42, 43, 567, 5 }; protected static final int ARRAY_LENGTH = array.length; public static void main(String[] args) { for(int i = 0; i < ARRAY_LENGTH - 1; i++) { for(int j = 0; j < ARRAY_LENGTH - 2; j++) { a = array[j]; b = array[j + 1]; if(a > b) { array[j] = b; array[j + 1] = a; } } } for(int i = 0; i < array.length - 1; i++) { System.out.print(array[i] + " "); } } }

Accepted Answer · 2016-10-12T16:50:58

BP internal cycle

  for(int i = 0; i < ARRAY_LENGTH - 1; i++) { for(int j = 0; j < ARRAY_LENGTH - 2; j++) { a = array[j]; b = array[j + 1]; if(a > b) { array[j] = b; array[j + 1] = a; } } }

The maximum index of an element that can be accessed is ARRAY_LENGTH - 2 . Therefore, the last element of the array remains "untouchable" :)

Imagine that the size of the array is 2. In this case, ARRAY_LENGTH - 2 will be 0. As a result, the inner loop will never be executed, and the array of two elements will not be sorted.

And besides, in this loop, you also incorrectly specified the upper limit of the index, so, again, the last element of the array is not displayed.

  for(int i = 0; i < array.length - 1; i++) { ^^^^^^^^^^^^^^^^^ System.out.print(array[i] + " ");

And if you enter the ARRAY_LENGTH constant, then use it everywhere instead of the member of the length class. Must be

  for(int i = 0; i < ARRAY_LENGTH; i++) { ^^^^^^^^^^^^ System.out.print(array[i] + " ");

rjhdby rjhdby 12.7k four 22 45 · Answer 2 · 2016-10-12T16:49:27

The last element of the array is lost here.

 for(int i = 0; i < array.length - 1; i++)

and here

 for(int i = 0; i < ARRAY_LENGTH - 1; i++) {

Why do you subtract one from the length if you compare it with the operator “strictly less”?

rjhdby

12.7k four 22 45

I do not miss it, because the array counter starts from zero, i.e. if the length of the array is 2, and I need to get the last element (the second), I need to subtract one from the length (2 - 1 = 1). - ikerya
@ikerya, Only here in the condition you have strictly more. If you subtract one, the condition must be greater than or equal to, and not strictly greater. - post_zeew pm
@ikerya is just your cycle, on two elements it will be executed only once - for i = 0, because at the next iteration you have i = 1, and the exit conditions i <(2-1) => i <1 are rjhdby

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Answer 3 · 2016-10-12T16:39:19

First, in the inner loop, you do not compare the last two elements of the array, since j < ARRAY_LENGTH - 2 .

Secondly, when displaying the elements of an array on the screen, you output all the elements, except for the last one, since you have i < array.length - 1 .

Romag romag 186 one eleven · Answer 4 · 2016-10-12T16:44:13

Here is the whole logic of your application.

 int[] arr = new int[]{90,123,12,0,1,4,7,44,-2,-4,-5}; int a = 0; int max = -50; int imax = -50; max = arr[0]; for (int i = 0;i<arr.length;i++){//Выполняется пока не кончаться элементы массива. for(a = i; a<arr.length;a++){//Находит максимальный элемент max = -50; if(max<arr[a]) { max = arr[a];//Меняет максимальный элемент imax = a;//Запоминает какой элемент массива максимальный } if(arr[i]<max){//Сравниваем максимальный элемент с текущим если он меньше то заменяем значения arr[imax]=arr[i];//Максимальный элемент = текущему arr[i] = max;//Текущий равен максмимальному } } } for (int ac = 0; ac<arr.length;ac++){ System.out.println(arr[ac]+" "); } }

You, probably, misunderstood me, I don’t need someone else’s code (the more so after killing if I understood correctly).
Since this is the last element, you skip it in this code: for (int i = 0; i <ARRAY_LENGTH - 1; i ++)

The sorting method does not work correctly.

4 answers 4

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