基础数据结构和算法三：Insertion Sort
public class Insertion { // use natural order and Comparable interface public static void sort(Comparable[] a) { int N = a.length; for (int i = 0; i < N; i++) { //showGUI(a); for (int j = i; j > 0 && less(a[j], a[j-1]); j--) { exch(a, j, j-1); // showGUI(a); } assert isSorted(a, 0, i); } assert isSorted(a); } // use a custom order and Comparator interface - see Section 3.5 public static void sort(Object[] a, Comparator c) { int N = a.length; for (int i = 0; i < N; i++) { for (int j = i; j > 0 && less(c, a[j], a[j-1]); j--) { exch(a, j, j-1); } assert isSorted(a, c, 0, i); } assert isSorted(a, c); } // return a permutation that gives the elements in a[] in ascending order // do not change the original array a[] public static int[] indexSort(Comparable[] a) { int N = a.length; int[] index = new int[N]; for (int i = 0; i < N; i++) index[i] = i; for (int i = 0; i < N; i++) for (int j = i; j > 0 && less(a[index[j]], a[index[j-1]]); j--) exch(index, j, j-1); return index; } /*********************************************************************** * Helper sorting functions ***********************************************************************/ // is v < w ? private static boolean less(Comparable v, Comparable w) { return (v.compareTo(w) < 0); } // is v < w ? private static boolean less(Comparator c, Object v, Object w) { return (c.compare(v, w) < 0); } // exchange a[i] and a[j] private static void exch(Object[] a, int i, int j) { Object swap = a[i]; a[i] = a[j]; a[j] = swap; } // exchange a[i] and a[j] (for indirect sort) private static void exch(int[] a, int i, int j) { int swap = a[i]; a[i] = a[j]; a[j] = swap; } /*********************************************************************** * Check if array is sorted - useful for debugging ***********************************************************************/ private static boolean isSorted(Comparable[] a) { return isSorted(a, 0, a.length - 1); } // is the array sorted from a[lo] to a[hi] private static boolean isSorted(Comparable[] a, int lo, int hi) { for (int i = lo + 1; i <= hi; i++) if (less(a[i], a[i-1])) return false; return true; } private static boolean isSorted(Object[] a, Comparator c) { return isSorted(a, c, 0, a.length - 1); } // is the array sorted from a[lo] to a[hi] private static boolean isSorted(Object[] a, Comparator c, int lo, int hi) { for (int i = lo + 1; i <= hi; i++) if (less(c, a[i], a[i-1])) return false; return true; } // print array to standard output private static void show(Comparable[] a) { for (int i = 0; i < a.length; i++) { System.out.println(a[i]); } }}
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