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

Java代码



public class Insertion {

public static void main(String[] args) {
int n = 20;
MyItem [] a = new MyItem
;
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);
}
}
}

public class Insertion {

	public static void main(String[] args) {
		int n = 20;
		MyItem [] a = new MyItem
;
		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。