最小堆代码实现
1 package sort; 2 3 import java.util.ArrayList; 4 import java.util.List; 5 6 /** 7 * 最小堆排序 8 * Created by liuwei on 16/3/7. 9 */ 10 public class MinHeap { 11 12 private List<Integer> heap = null; 13 14 public MinHeap(){ 15 heap = new ArrayList<>(); 16 } 17 18 public MinHeap(int[] nums){ 19 heap = new ArrayList<>(nums.length); 20 for(int i=0; i<nums.length;i++){ 21 heap.add(nums[i]); 22 } 23 adjust(); 24 } 25 26 public void addElement(int number){ 27 heap.add(number); 28 // adjust(); 29 adjustFromDownToUp(); 30 } 31 32 public int size(){ 33 return heap.size(); 34 } 35 36 public boolean isEmpty(){ 37 for(Integer i : heap){ 38 return false; 39 } 40 return true; 41 } 42 43 public Integer getTop(){ 44 return isEmpty()? null:heap.get(0); 45 } 46 47 public Integer delTop(){ 48 if(isEmpty()) return null; 49 int top = heap.remove(0); 50 if(!isEmpty()){ 51 heap.add(0,heap.get(heap.size()-1)); 52 heap.remove(heap.size()-1); 53 // adjust(); 54 adjustFromUpToDown(); 55 } 56 return top; 57 } 58 59 private void swap(int i,int j){ 60 int tmp = heap.get(i); 61 heap.set(i,heap.get(j)); 62 heap.set(j,tmp); 63 } 64 65 /** 66 * 全局调整 67 * */ 68 private void adjust(){ 69 if(size() <= 1) return; 70 int i = size() - 1; 71 int parent = 0; 72 if(i % 2 == 1){ 73 parent = (i -1) / 2; 74 if(heap.get(i) < heap.get(parent)){ 75 swap(i,parent); 76 } 77 i--; 78 } 79 while(i > 0){ 80 parent = (i - 1) / 2; 81 int value = Math.min(heap.get(i-1),heap.get(i)); 82 if(value < heap.get(parent)){ 83 if(value == heap.get(i-1)){ 84 swap(i-1,parent); 85 } 86 else{ 87 swap(i,parent); 88 } 89 } 90 i= i -2; 91 } 92 } 93 94 //当删除一个元素的时候,是将最后一个元素,插入到之前第一个元素的位置,该元素后面是有序的,这时候自上向下调整 95 private void adjustFromUpToDown(){ 96 if(size() < 2) return; 97 int index = 0; 98 int left = 2 * index + 1; 99 int right = 2 * index + 2; 100 while(index < size() ){ 101 if(right < size()){ 102 int value = Math.min(heap.get(left),heap.get(right)); 103 if(value < heap.get(index)){ 104 if(value == heap.get(left)){ 105 swap(left,index); 106 index = left; 107 } 108 else{ 109 swap(right,index); 110 index = right; 111 } 112 left = 2 * index + 1; 113 right = 2 * index + 2; 114 } 115 else{ 116 return; 117 } 118 } 119 else if(left < size()){ 120 if(heap.get(left) < heap.get(index)){ 121 swap(left,index); 122 } 123 return; 124 } 125 else{ 126 return; 127 } 128 } 129 } 130 131 //当增加一个元素的时候,是插入到最后一个位置,这时候,前面是有序的,这时候自下而上的调整 132 private void adjustFromDownToUp(){ 133 if(size() < 2) return; 134 int index = heap.size() - 1; 135 int parent = (index - 1) / 2; 136 if(index % 2 == 1){ 137 if(heap.get(index) < heap.get(parent)){ 138 swap(index,parent); 139 index = parent; 140 } 141 else{ 142 return; 143 } 144 } 145 int left = 0, right = 0; 146 while(index > 0){ 147 parent = (index - 1)/2; 148 if(index % 2 == 1){ 149 left = index; 150 right = index + 1; 151 } 152 else{ 153 left = index - 1; 154 right = index; 155 } 156 int value = Math.min(heap.get(left),heap.get(right)); 157 if(value < heap.get(parent)){ 158 if(value == heap.get(left)){ 159 swap(left,parent); 160 } 161 else{ 162 swap(right,parent); 163 } 164 index = parent; 165 } 166 else{ 167 return; 168 } 169 } 170 } 171 172 173 public void show(){ 174 for(Integer i : heap){ 175 System.out.print(i+" "); 176 } 177 System.out.println(); 178 } 179 180 public static void main(String[] args) { 181 int[] nums = {9,12,17,30,50,20,60,65,4}; 182 MinHeap heap = new MinHeap(); 183 // heap.show(); 184 // heap.addElement(49); 185 // heap.show(); 186 // while(!heap.isEmpty()){ 187 // System.out.print(heap.delTop()+" "); 188 // } 189 // System.out.println(); 190 191 for(int i=0; i<nums.length;i++){ 192 heap.addElement(nums[i]); 193 // heap.show(); 194 } 195 196 while(!heap.isEmpty()){ 197 System.out.print(heap.delTop()+" "); 198 } 199 System.out.println(); 200 } 201 }