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package com.manni;/** *  * @date 2014-04-12 * @author fei.cheng * */public class PriorityQueue {    private int[] Q;    private int capacity;    public PriorityQueue(int initialCapacity) {        Q = new int[initialCapacity+1];        Q[0] = 0;        this.capacity = initialCapacity;    }        public int size() {        return Q[0];    }        public int capacity() {        return capacity;    }        public int top() {        if (Q[0] == 0) {            System.out.println("Empty queue, no element.");            System.exit(-1);        }        return Q[1];    }    public int pop() {        if (Q[0] == 0) {            System.out.println("Empty queue, no element.");            System.exit(-1);        }        int value = Q[1];        Q[1] = Q[Q[0]--];        shiftdown(Q[0]);        return value;    }        public void push(int value) {        if (Q[0] == capacity()) {            Q = enlargeCapacity();        }        Q[++Q[0]] = value;        shiftup(Q[0]);    }        private int[] enlargeCapacity() {        this.capacity = 2 * Q[0] + 1;        int[] new_Q = new int[capacity];        for(int i = 0; i <= Q[0]; ++i) {            new_Q[i] = Q[i];        }        return new_Q;    }        private void swap(int i, int j) {        int tmp = Q[i];        Q[i] = Q[j];        Q[j] = tmp;    }        private void shiftdown(int n) {        int idx = 1;        while (2*idx <= n) {            int left = 2*idx;            int right = left+1;            int son = left;            if ((right <= n) && (Q[right] < Q[left])) {                son = right;            }            if(Q[idx] > Q[son]) {                swap(idx, son);                idx = son;            } else {                break;            }        }    }        private void shiftup(int n) {        int idx = n;        while (idx/2 >= 1) {            int father = idx/2;            if (Q[idx] < Q[father]) {                swap(idx, father);                idx = father;            } else {                break;            }        }    }}class Test {    public static void main(String[] args) {        PriorityQueue pq = new PriorityQueue(4);                pq.push(23);        pq.push(10);        pq.push(19);        pq.push(25);        pq.push(34);        pq.push(85);        pq.push(88);                System.out.println(pq.pop());        System.out.println(pq.pop());        System.out.println(pq.pop());        System.out.println(pq.pop());        System.out.println(pq.pop());        System.out.println(pq.pop());        System.out.println(pq.pop());        System.out.println(pq.pop());    }}
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