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PriorityQueue.java
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105 lines (91 loc) · 2.11 KB
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public class PriorityQueue {
final static int BaseLen = 15;
final static int IncreaseLen = 10;
int size = BaseLen;
int length = 0;
int[] arr = new int[BaseLen];
public PriorityQueue() {
}
public void insert(int key) {
if (length + 1 > arr.length) {
int[] temp = new int[length];
for(int i = 0; i < length; ++i )
temp[i] = arr[i];
arr = new int[size = length+IncreaseLen];
for(int i = 0; i < length; ++i )
arr[i] = temp[i];
}
arr[length] = Integer.MIN_VALUE;
length = length + 1;
increaseKey(length, key);
}
public void increaseKey(int i, int key) {
i = i - 1;
if (key < arr[i])
System.out.println("插入的数小于原来的数");
arr[i] = key;
int p = (i + 1) / 2 - 1; // 父节点
while (i > 0 && arr[p] < arr[i]) {
int t = arr[i];
arr[i] = arr[p];
arr[p] = t;
i = p;
p = (i + 1) / 2 - 1;
}
}
public int maximum() {
if (length == 0) {
System.out.println("队列中没有加入元素");
return 0;
}
return arr[0];
}
public int extractMax() {
if (length == 0) {
System.out.println("队列中没有加入元素");
return 0;
}
int max = arr[0];
length--;
arr[0] = Integer.MIN_VALUE;
maxHeapIfy(1);
return max;
}
public void maxHeapIfy(int i) {
int l = 2 * i - 1; // left左节点
int r = 2 * i;// 右节点
i = i - 1;
int largest = 0;
if (l < arr.length && arr[l] > arr[i])
largest = l;
else
largest = i;
if (r < arr.length && arr[r] > arr[largest])
largest = r;
if (largest != i) {
int t = arr[i];
arr[i] = arr[largest];
arr[largest] = t;
maxHeapIfy(largest + 1);
}
}
public static void main(String[] args) {
PriorityQueue q = new PriorityQueue();
System.out.println("插入队列的数字:12,3,4,8,13,20,16,15,22,17");
q.insert(12);
q.insert(3);
q.insert(4);
q.insert(8);
q.insert(13);
q.insert(20);
q.insert(16);
q.insert(15);
q.insert(22);
q.insert(17);
System.out.println("最大值："+q.maximum());
q.increaseKey(3, 30);
System.out.println("在第3个位置插入30后的最大值："+q.maximum());
System.out.println("取出最大值："+q.extractMax());
System.out.println("取出后的最大值："+q.maximum());
}
}