java算法:插入排序
java算法:插入排序
如,对EXAMPLE 字母进行排序:
E X A M P L E 开始
E [X] A M P L E E<X 不变
[A] E X M P L E A < E:A插入到E前
A E [M] X P L E ...
A E M [P] X L E
A E [L] M P X E
A E [E] L M P X
- public class Insertion {
- public static void main(String[] args) {
- int n = 20;
- MyItem [] a = new MyItem[n];
- for (int i = 0; i < n; i++) {
- a[i] = new MyItem();
- a[i].rand();
- }
- for (int i = 0; i < n; i++) {
- System.out.print(a[i] + " ");
- }
- insertion(a, 0, n);
- System.out.println("");
- print(a, n);
- }
- private static void print(MyItem a [], int n){
- for (int i = 0; i < n; i++) {
- System.out.print(a[i] + " ");
- }
- }
- public static void insertion(MyItem [] a, int l, int r){
- int i;
- for(i = r - 1; i >= l + 1; i--){
- compExch(a, i-1, i);
- }
- for (i = l + 2; i < r; i++){
- int j = i;
- MyItem v = a[i];
- while(less(v, a[j - 1])){
- a[j] = a[j - 1];
- j--;
- }
- a[j] = v;
- }
- }
- public static boolean less(Item v, Item w){
- return v.less(w);
- }
- public static void exch(Item [] a, int i, int j){
- Item t = a[i];
- a[i] = a[j];
- a[j] = t;
- }
- public static void compExch(Item [] a, int i, int j){
- if(less(a[j],a[i])){
- exch(a, i, j);
- }
- }
- }
插入排序的运行时间主要依赖于输入文件中关键字的最初顺序。如,文件很大而且关键字已经排好(或者几乎排好),那么插入排序运算就很快了,而选择排序运行却很慢。