数组操作（排序、平均值、偶置前奇置后）

import java.util.Arrays;

public class Qiao{
public static void swap(int [] a,int i,int j)
{
int t=a[i];
a[i]=a[j];
a[j]=t;
}

public static void bubbleSort(int[] a){
	for(int i=0;i<a.length;i++){
		boolean sorted =true;
		for(int j=1;j<a.length-i;j++){
			if(a[j-1]>a[j]){
				swap(a,j-1,j);
				sorted=false;
			}
		}
		if(sorted==true){
			return;
		}
	}
}


public static void bubbleSort1(int[]a){
	for(int i=0;i<a.length;i++){
		for(int j=a.length-1;j>i;j--){
			if(a[j]<a[j-1]){
				swap(a,j,j-1);
			}
		}
	}
}


//去掉一个最大值和做小值计算平均值
public static double average(int [] a){
	int sum=0;
	int max=Integer.MIN_VALUE;
	int min=Integer.MAX_VALUE;
	for(int v:a){
		sum+=v;
		
		if(v>max){
			max=v;
		}
		if(v<min){
			min=v;
		}
	}
	return (double)(sum-max-min)/(a.length-2);//强制类型转换
}

public static void testBubbleSort(int[]a){
	System.out.println("排序前");
System.out.println(Arrays.toString(a));
	bubbleSort1(a);
	System.out.println("排序后");
System.out.println(Arrays.toString(a));
}



public static int[] rotate(int[] nums, int k) {
	k = k % nums.length;
	int[] rightPart = Arrays.copyOfRange(nums, nums.length - k, nums.length);
	//System.out.println(Arrays.toString(rightPart));
	System.arraycopy(nums, 0, nums, k, nums.length - k);
	//System.out.println(Arrays.toString(nums));
	System.arraycopy(rightPart, 0, nums, 0, k);

	return nums;
}


//函数实现偶数置前，奇数置后
//前后各值一个，begin从前往后走，偶数继续，奇数停下，
//end 从后往前，遇到偶数停下，
//交换begin和end，begin++,end--
public static int[] partition1(int[] nums){
	int begin=0;
	int end=nums.length-1;
	//[begin,end]的数是未判断的数
	//[0,begin)偶数
	//[end,nums.length)奇数
	while(begin<end){
		while(begin<end&&nums[begin]%2==0){
			begin++;
		}
		while(begin<end&&nums[begin]%2!=0){
			end--;
		}
		swap(nums,begin,end);
	}
	return nums;
}

//函数实现偶数置前，奇数置后,都从头开始，i++，遇到偶数停下，与d值交换后，i++，j++;
public static int [] partition2(int []nums){
	int d=0;
	for(int i=0;i<nums.length;i++){
		if(nums[i]%2==0){
			swap(nums,i,d);
			d++;
		}
	}
	return nums;
}


public static void main(String[] args){
	int[]a={1,2,3,4,5,6,7};
	int[]b={7,6,5,4,3,2,1};
	int[]c={7,5,4,3,1,2,6};
	int[]d={4,4,4,4,4,4,4};
	
	
	testBubbleSort(a);
	testBubbleSort(b);
	testBubbleSort(c);
	testBubbleSort(d);
	
	System.out.println(average(new int[] { 1, 2, 3, 4, 5, 6, 7 }));
	
	System.out.println(Arrays.toString(rotate(new int[] { 1, 2, 3, 4, 5 },3)));
	
	System.out.println(Arrays.toString(rotate(new int[] { 1, 2, 3, 4, 5 },8)));
	
	System.out.println(Arrays.toString(rotate(new int[] { 1, 2, 3, 4, 5, 6, 7 },8)));
	
	System.out.println(Arrays.toString(partition2(new int[] { 1, 2, 3, 4, 5, 6, 7, 8, 9})));
}

}