堆实现一个大根堆

水深无声 2022-12-04 09:27 186阅读 0赞

# 数据结构——堆 #

--------------------

**creat —— 创建堆  
show —— 按层输出堆  
push —— 入堆  
pop —— 出堆  
getTop —— 拿堆顶**

public class test {
        
    
        public static void main(String[] args) {
        
            TestHeap testHeap = new TestHeap();
            int[] array = {
        27, 15, 19, 18, 28, 34, 65, 49, 25, 37};
            testHeap.creatHeap(array);
            testHeap.show();
            testHeap.push(80);
            testHeap.show();
            testHeap.pop();
            testHeap.show();
            System.out.println(testHeap.getTop());
        }

**out：**  
65 49 34 25 37 27 19 18 15 28  
80 65 34 25 49 27 19 18 15 28 37  
65 49 34 25 37 27 19 18 15 28  
65

package 堆;
    
    
    import java.util.Arrays;
    
    /**
     * @author ：ZXY
     * @date ：Created in 2020/9/6 17:59
     * @description：
     */
    
    
    public class TestHeap {
        
        public int[] elem;
        public int usedSize;
        public TestHeap() {
        
            this.elem=new int[10];
            this.usedSize=0;
        }
    
    
        //创建堆
        public void creatHeap(int[] array){
        
            for(int i=0;i<array.length;i++){
        
                this.elem[i]=array[i];
                this.usedSize++;
            }
            // i 表示每棵子树的根节点
           for(int i=(this.usedSize-1-1)/2;i>=0;i--){
        
               adjustDown(i,this.usedSize);
            }
        }
    
    
        //向下调整  root每棵子树根节点  len每棵子树结束位置
        public void adjustDown(int root,int len){
        
            int parent=root;
            int child=2*parent+1;
            while (child<len){
        
                //1、找到左右孩子的最大值
                if((child+1<len) && this.elem[child]<this.elem[child+1]){
        
                    child=child+1;
                }
                //child保存左右孩子最大值下标
    
                if(this.elem[child]>this.elem[parent]){
        
                    int tmp=this.elem[child];
                    this.elem[child]=this.elem[parent];
                    this.elem[parent]=tmp;
                    parent=child;
                    child=2*parent+1;
                }else{
        
                    //不需进行调整
                    break;
                }
            }
        }
    
    	//添加元素
        public  void push(int val){
        
            if(isFull()){
        
                this.elem=Arrays.copyOf(this.elem,2*this.elem.length);
            }
            this.elem[usedSize]=val;
            this.usedSize++;
            adjustUp(this.usedSize-1);
        }
        public boolean isFull(){
        
            return this.usedSize==this.elem.length;
        }
        
        //向上调整
        public void adjustUp(int child) {
        
            int parent=(child-1)/2;
            while(child>0){
        
                if(this.elem[child]>this.elem[parent]){
        
                    int tmp=this.elem[child];
                    this.elem[child]=this.elem[parent];
                    this.elem[parent]=tmp;
                    child=parent;
                    parent=(child-1)/2;
                }else {
        
                    break;
                }
            }
        }
    
    
    
        public void show(){
        
            for (int i = 0; i <this.usedSize ; i++) {
        
                System.out.print(this.elem[i]+" ");
            }
            System.out.println();
        }
    
    
        //删除堆顶
        public void pop(){
        
            if(isEmpty()){
        
                System.out.println("堆为空");
            }
            this.elem[0]=this.elem[this.usedSize-1];
            this.usedSize--;
            adjustDown(0,this.usedSize);
        }
        public boolean isEmpty(){
        
            return this.usedSize==0;
        }
    
    	//得到堆顶
        public int getTop(){
        
            if(isEmpty()){
        
                System.out.println("堆为空");
            }
            return this.elem[0];
        }
    }