creating a max-heap using java

Question

I am trying to create a Max-Heap in java using the following code: ``` public class Heapify { // 16 14 10 8 7 9 3 2 4 1 public static int[] Arr = {4, 1, 3, 2, 16, 9, 10, 14, 8, 7}; public static int counter = 0; public static void main(String[] args) { int kk; for (kk = 0; kk <= Arr.length - 1; kk++) { heapM(Arr, kk); } for (int krk = 0; krk < Arr.length; krk++) { System.out.println(Arr[krk]); } } public static void heapM(int[] Arr, int i) { int largest; int left = i * 2; int right = i * 2 + 1; if (((left < Arr.length) && (Arr[left] > Arr[i]))) { largest = left; } else { largest = i; } if (((right < Arr.length) && (Arr[right] > Arr[largest]))) { largest = right; } if (largest != i) { swap(i, largest); heapM(Arr, largest); } } private static void swap(int i, int largest) { int t = Arr[i]; Arr[i] = Arr[largest]; Arr[largest] = t; } } ``` The desired output should be : ``` 16 14 10 8 7 9 3 2 4 1 ``` Whereas I am getting ``` 4 3 16 14 8 9 10 2 1 7 ``` Can someone please help as to why the…

Accepted Answer

I ran your code, and in addition to what Jodaka said, I found one more error

```
for (kk = 0; kk <= Arr.length - 1; kk++) {
        heapM(Arr, kk);
}
```

should be

```
for (kk = Arr.length -1; kk >= 0; kk--) {
        heapM(Arr, kk);
}
```

because when doing MaxHepify, you start from the end, and go backwards. and

```
 int left = i * 2;
 int right = i * 2 + 1;
```

should be, as Jodaka said

```
int left = 2*i+1;
int right = 2*i + 2;
```

I ran it here and the output is now correct

creating a max-heap using java

Solution

Problem