看见别人写出来美丽有用的代码，最终下定决心好好学习算法，在这里记录下自己学习的成果。
前两天看到数组的全排列，于是自己照着别人的想法实现了一下，感觉自己理解了，有点小高兴，记载一下。
/*
* 数组的全排列*/
public class myAllSort {
public static void sort(int[] number,int start,int end){
int temp;
// 假设发现数组对掉元素到了最后一个，那么就输出，证明已经符合要求
if(start==end)
{
print(number);
}
// 依次将数组的第一个元素和后面的元素一一对调，然后第一次对掉之后递归，
// 将数组的第二个元素和他之后的元素对掉，最后一次进行
/*
* 1 2 3 4-->1 2 3 4-->1 2 3 4
* 1 2 4 3
* 1 3 2 4-->1 3 2 4
* 1 3 4 2
* 1 4 3 2-->1 4 3 2
* 1 4 2 3
* 2 1 3 4
* 3 2 1 4
* 4 2 3 1
* */
for(int i=start;i<end;i++){
temp = number[start];
number[start] = number[i];
number[i] = temp;
sort(number,start+1,end);
// print(number); //输出排序的全过程
// 将对掉之后的数组便会原来的顺序，以便下次
temp = number[start];
number[start] = number[i];
number[i] = temp;
//
}
}
public static void print(int[] number){
for(int i=0;i<number.length;i++)
{
System.out.print(number[i]+"--");
}
System.out.println();
}
public static void main(String[] args) {
int[] number = {1,2,3,4};
sort(number,0,number.length);
}
}另一种数组的选择排序方法，感觉这个思想对我非常实用，详细的出处给忘了。
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
/*
* 从属注重选择几个数字进行排列
* 比如：五个选三个的全排列
* 算法原理：在数组中选取一个数字先存储到集合中，然后再依次选取其它数字，
* */
public class ChooseServalFromNumber {
public static final int NUM = 4;
public static void main(String[] args) {
Object[] obj = new String[]{"1","2","3","4"};
List<Object> list = Arrays.asList(obj);
chooseNumberSort(list,new ArrayList<Object>());
}
public static void chooseNumberSort(List<Object> list,List<Object> target){
// 假设目标集合中的数字达到了我们需求的个数就输出
// if(target.size()==NUM)
// System.out.println(target+"--");
if(target.size()==4)
System.out.println(list+" --> "+target+"--输出");
// else
// System.out.println(list+" --> "+target);
for(int i=0;i<list.size();i++){
List<Object> newList = new ArrayList<Object>(list);
List<Object> newTarget = new ArrayList<Object>(target);
newTarget.add(newList.get(i));
newList.remove(i);
System.out.println(list+" --> "+target);
chooseNumberSort(newList,newTarget);
}
}
}
/*
输出结果：
[1, 2, 3, 4] --> []
[2, 3, 4] --> [1]
[3, 4] --> [1, 2]
[4] --> [1, 2, 3]
[] --> [1, 2, 3, 4]--输出
[3, 4] --> [1, 2]
[3] --> [1, 2, 4]
[] --> [1, 2, 4, 3]--输出
[2, 3, 4] --> [1]
[2, 4] --> [1, 3]
[4] --> [1, 3, 2]
[] --> [1, 3, 2, 4]--输出
[2, 4] --> [1, 3]
[2] --> [1, 3, 4]
[] --> [1, 3, 4, 2]--输出
[2, 3, 4] --> [1]
[2, 3] --> [1, 4]
[3] --> [1, 4, 2]
[] --> [1, 4, 2, 3]--输出
[2, 3] --> [1, 4]
[2] --> [1, 4, 3]
[] --> [1, 4, 3, 2]--输出
[1, 2, 3, 4] --> []
[1, 3, 4] --> [2]
[3, 4] --> [2, 1]
[4] --> [2, 1, 3]
[] --> [2, 1, 3, 4]--输出
[3, 4] --> [2, 1]
[3] --> [2, 1, 4]
[] --> [2, 1, 4, 3]--输出
[1, 3, 4] --> [2]
[1, 4] --> [2, 3]
[4] --> [2, 3, 1]
[] --> [2, 3, 1, 4]--输出
[1, 4] --> [2, 3]
[1] --> [2, 3, 4]
[] --> [2, 3, 4, 1]--输出
[1, 3, 4] --> [2]
[1, 3] --> [2, 4]
[3] --> [2, 4, 1]
[] --> [2, 4, 1, 3]--输出
[1, 3] --> [2, 4]
[1] --> [2, 4, 3]
[] --> [2, 4, 3, 1]--输出
[1, 2, 3, 4] --> []
[1, 2, 4] --> [3]
[2, 4] --> [3, 1]
[4] --> [3, 1, 2]
[] --> [3, 1, 2, 4]--输出
[2, 4] --> [3, 1]
[2] --> [3, 1, 4]
[] --> [3, 1, 4, 2]--输出
[1, 2, 4] --> [3]
[1, 4] --> [3, 2]
[4] --> [3, 2, 1]
[] --> [3, 2, 1, 4]--输出
[1, 4] --> [3, 2]
[1] --> [3, 2, 4]
[] --> [3, 2, 4, 1]--输出
[1, 2, 4] --> [3]
[1, 2] --> [3, 4]
[2] --> [3, 4, 1]
[] --> [3, 4, 1, 2]--输出
[1, 2] --> [3, 4]
[1] --> [3, 4, 2]
[] --> [3, 4, 2, 1]--输出
[1, 2, 3, 4] --> []
[1, 2, 3] --> [4]
[2, 3] --> [4, 1]
[3] --> [4, 1, 2]
[] --> [4, 1, 2, 3]--输出
[2, 3] --> [4, 1]
[2] --> [4, 1, 3]
[] --> [4, 1, 3, 2]--输出
[1, 2, 3] --> [4]
[1, 3] --> [4, 2]
[3] --> [4, 2, 1]
[] --> [4, 2, 1, 3]--输出
[1, 3] --> [4, 2]
[1] --> [4, 2, 3]
[] --> [4, 2, 3, 1]--输出
[1, 2, 3] --> [4]
[1, 2] --> [4, 3]
[2] --> [4, 3, 1]
[] --> [4, 3, 1, 2]--输出
[1, 2] --> [4, 3]
[1] --> [4, 3, 2]
[] --> [4, 3, 2, 1]--输出
*/