# Sort algorithm Four: heap sort Heapsort

Source: Internet
Author: User

`1 /**2 * Heap sequencing ideas: O (NLOGN)3 * Use the maximum heap, pass in an array, first use the number to build the heap, maintain the nature of the heap4 * Replace the first number with the last number in the heap, because the first number is the largest5 * Reduce the size of the heap by one6 * Then maintain the heap's nature on the heap size7 * Repeat Operation :8  *    9  *    Ten  */ One  Public  classHeapsort A { -     /** - * Static variable holds the size of the heap the      */ -     Private  Static  intheapsize = 0 ;  -  -     /** + * Heap Sort Master Method - * Build the largest heap and then sort the heap + * Heap sequencing is to place the topmost largest element at the bottom and then maintain the properties of the maximum heap above A      */  at      Public  Static  voidHeapsort (int[] resoucearr) -     { -         //the size of the heap -HeapSize = resoucearr.length-1 ; -  - _buildmaxheap (Resoucearr); in  -          for(inti = resoucearr.length-1; I >= 0; i--) to         { +             inttemp = resoucearr[0] ; -Resoucearr[0] =Resoucearr[i]; theResoucearr[i] =temp; *              \$HeapSize = heapsize-1 ; Panax Notoginseng_maxheapify (Resoucearr, 0 );  -         } the     } +  A     /** the * Build Maximum heap + * After construction is not orderly, but in line with the maximum heap nature, the above number must be greater than the number below -      */ \$     Private  Static  void_buildmaxheap (int[] arr) \$     { -         intLength = Arr.length-1 ;  -  the         //starting from the penultimate row to maintain the maximum heap properties -         //when HeapSize is an even number, heapsize is reduced by oneWuyi         //when the heapsize is odd, it does not change the         if(length% 2 = = 0) -         { Wulength--; -         } About          for(inti = LENGTH/2; I >= 0; i--) \$         { - _maxheapify (arr, i); -         } -     } A  +     /** the * For maintaining the nature of the heap - * Tree-shaped heap in postion position down to maintain the nature of the heap, from postion down to meet the maximum heap properties \$      */ the     Private  Static  void_maxheapify (int[] arr,intpostion) the     { the         //calculate Postion's left child and right child thepostion = postion + 1 ; -  in         intL = postion * 2-1;  the         intr = postion * 2 ; thepostion = postion-1 ; About  the         intlargest =Maxnuminthreenum (arr, postion, L, R); the  the         //if the maximum heap property is not met, the value is exchanged and then the maximum heap property is checked under the tree +         if(Largest <=heapsize) -         {     the             if(Largest! =postion)Bayi             { the                 //Exchange maximum value with parent node value the                 inttemp =Arr[postion]; -Arr[postion] =Arr[largest]; -Arr[largest] =temp; the                 //If the child node changes, rebuild the largest heap that has child nodes as root the _maxheapify (arr, largest);  the  the             } -         } the     }     the  the     /**94 * Compare three numbers in an array to find the maximum value the      */ the     Private  Static  intMaxnuminthreenum (int[] arr,intAintBintc) the     {98         intMax =A; About         //the array length is smaller than the left child, and the maximum value is itself -         if(HeapSize <b)101         {102Max =A;103         }104         Else if(HeapSize >=b && heapsize <c) the         {106             if(Arr[a] <Arr[b])107             {108Max =b;109             } the         }111         Else the         {113             if(Arr[a] >Arr[b]) the             { theMax =A; the             }117             Else118             {119Max =b; -             }121             if(Arr[max] <Arr[c])122             {123Max =C;124             }             the         }126         returnMax;127     }     -}`

Sort algorithm Four: heap sort Heapsort

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