排序算法的成本模型计算的是比较和交换的次数。好的排序算法应该尽量避免元素的交换。

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/**
 * 交换
 */
public static void exch(Comparable[] a, int i, int j) {
    Comparable temp = a[i];
    a[i] = a[j];
    a[j] = temp;
}

private void exch(int i, int j) {
    Key t = pq[i];
    pq[i] = pq[j];
    pq[j] = t;
}

/**
 * 比较
 */
public static boolean less(Comparable a, Comparable b) {
    return a.compareTo(b) < 0;
}

private boolean less(int i, int j) {
    return pq[i].compareTo(pq[j]) < 0;
}