[英]HeapSort Algorithm Indexed 1 through n, and actual code has to be from 0 to n-1
I'm kind of new to algorithms and wanted to implement heap sort algorithm. 我对算法有点陌生,想实现堆排序算法。 The algorithm is given as follows: 该算法如下:
Parent(i) return Math.floor(i/2) 父级(i)返回Math.floor(i / 2)
Left(i) return 2i Left(i)返回2i
Right(i) return 2i+1 向右(i)返回2i + 1
Then there is HEAPIFY method that restores the heep property. 然后有HEAPIFY方法可还原heep属性。 Algorithm is as follows: 算法如下:
HEAPIFY(A, i)
l = Left(i)
r = Right(i)
if (l <= heap-size[A] and A[l] > A[i]
then largest = l
else largest = i
if r <= heap-size[A] and A[r] > A[largest]
then largest = r
if largest != i
then exchange A[i] <-> A[largest]
HEAPIFY(A, largest)
My Code that implements this method is: 我实现此方法的代码是:
public static void HEAPIFY(int[] A, int i) {
int l = LEFT(i);
int r = RIGHT(i);
int largest = 0;
if (l < A.length && A[l] > A[i]) {
largest = l;
} else {
largest = i;
}
if (r < A.length && A[r] > A[largest]) {
largest = r;
}
if (largest != i) {
int temp = A[i];
A[i] = A[largest];
A[largest] = temp;
HEAPIFY(A, largest);
}
}
Now My question is in the book algorithm is shown by drawing the tree of heap and array so for example array is: [16,14,10,8,7,9,3,2,4,1] and for the tree and also for array it is indexed starting from 1 to n, so Array[1] = 16 and in coding Array[0] = 16. Now i can not adjust the heapify method to start either from index 1 and go up to 1 or somehow make it start from 0 and let the heap be indexed from 0 to n-1. 现在我的问题在书中,算法是通过绘制堆树和数组树来显示的,例如,数组为:[16,14,10,8,7,9,3,2,4,1]并为树和同样对于数组,它的索引是从1到n,因此Array [1] = 16并在编码Array [0] = 16时。现在,我无法调整heapify方法以从索引1开始并升至1或以某种方式使它从0开始,并使堆从0索引到n-1。
Sorry if its kind of confusing i'm still confused but i would really appreciate some help. 对不起,如果仍然感到困惑,我仍然感到困惑,但是我将非常感谢您的帮助。
Thank you guys 感谢大伙们
Now HEAPIFY works and the following code is code to build the heap: 现在,HEAPIFY可以工作了,下面的代码是构建堆的代码:
public static void BUILD_HEAP(int[] A) {
heapSize = A.length;
for (int i = (int) Math.floor(A.length / 2.0); i >= 0; i--) {
HEAPIFY(A, i);
}
}
build heap also works and the only method that doesnot work is heapsort. 构建堆也可以工作,唯一不起作用的方法是堆排序。
public static void HEAPSORT(int[] A) {
BUILD_HEAP(A);
for (int i = A.length-1; i >= 1; i--) {
int temp = A[0];
A[0] = A[i];
A[i] = temp;
heapSize = heapSize-1;
HEAPIFY(A,0);
}
}
this has to sort but when i try to traverse the array after the call of heapsort it does not give the sorted array. 这必须进行排序,但是当我在调用heapsort之后尝试遍历数组时,它没有给出已排序的数组。 any ideas how to fix heapsort? 任何想法如何解决堆排序?
Parent(i) return Math.floor(i/2) 父级(i)返回Math.floor(i / 2)
=> Parent(i) return Math.floor((i - 1) / 2) => Parent(i)返回Math.floor((i-1)/ 2)
Left(i) return 2i Left(i)返回2i
=> Left(i) return 2i + 1 => Left(i)返回2i + 1
Right(i) return 2i+1 向右(i)返回2i + 1
=> Right(i) return 2i + 2 => Right(i)返回2i + 2
You can work this out either by fiddling around (which is what I actually did) or considering j = i - 1. 您可以通过摆弄(这是我实际上所做的)或考虑j = i-1来解决。
If i' = 2 i and j = i - 1 so i = j + 1 如果i'= 2 i并且j = i-1则i = j + 1
j' = i' - 1 = (2i) - 1 = (2(j + 1)) - 1 = 2j + 1 j'= i'-1 =(2i)-1 =(2(j + 1))-1 = 2j + 1
if you want to start form index 1,then you can initialize the array like this: [-x,16,14,10,8,7,9,3,2,4,1] -x is the array[0],in other words,you can ignore the element which is in array[0]. 如果要启动表格索引1,则可以这样初始化数组:[-x,16,14,10,8,7,9,3,2,4,1] -x是数组[0] ,换句话说,您可以忽略array [0]中的元素。
if you want to start form index 0,then you have to modify the function LEFT(i) and RIGHT(i). 如果要开始从索引0开始,则必须修改函数LEFT(i)和RIGHT(i)。
LEFT(i) return 2*i+1; LEFT(i)返回2 * i + 1;
RIGHT(i) return 2*i+2; RIGHT(i)返回2 * i + 2;
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