幾種排序算法的Java實現

結論：

代碼：

import java.util.Scanner;

public class Sort{
    public static void swap(int[] arr,int a,int b){
        arr[a]=arr[a]+arr[b];
        arr[b]=arr[a]-arr[b];
        arr[a]=arr[a]-arr[b];
    }

    /***
     * 穩定，O(n²)
     */
    public static void bubbleSort(int[] nums){
        int N = nums.length;
        for(int i=0;i<N;i++){
            for(int j=0;j<N-1-i;j++){
                if(nums[j]>nums[j+1]){
                    swap(nums,j,j+1);
                }
            }
        }
        System.out.println("bubble:");
        for(int i=0;i<N;i++){
            System.out.print(nums[i]+" ");
        }

    }

    /**
     * 不穩定，O(n²)
     */
    public static void selectSort(int[] nums){
        int N = nums.length;
        for(int i=0;i<N;i++){
            int MIN = i;
            for(int j=i+1;j<N;j++){
                if(nums[j]<nums[MIN]){
                    MIN = j;
                }
            }
            swap(nums, i, MIN);
        }
        System.out.println('\n'+"select:");
        for(int i=0;i<N;i++){
            System.out.print(nums[i]+" ");
        }

    }

    /**
     * 穩定，O(n²)
     */
    public static void insertSort(int[] nums) {
        int N = nums.length;
        for(int i=1;i<N;i++){
            for(int j=i;j>0&&nums[j]<nums[j-1];j--){
                swap(nums,j,j-1);
            }
            
        }
        System.out.println("\n"+"inset:");
        for(int i=0;i<N;i++){
            System.out.print(nums[i]+" ");
        }

    }

    /**
     * 不穩定，O(n)-O(n²)
     */
    public static void shellSort(int[] nums){
        int gap;
        int N = nums.length;
        for(gap=N/2;gap>0;gap/=2){
            for(int i=gap;i<N;i++){
                for(int j=i-gap;j>=0&&nums[j]>nums[j+gap];j-=gap){
                    swap(nums, j, j+gap);
                }
            }
        }
        System.out.println("\n"+"shell:");
        for(int i=0;i<N;i++){
            System.out.print(nums[i]+" ");
        }
    }

    /**
     * 不穩定，O(nlogn)
     */
    public static void quickSort(int[] nums){
        int low = 0,high=nums.length-1;
        quickSort(nums, low, high);
        System.out.println("\n"+"quick:");
        for(int i=0;i<nums.length;i++){
            System.out.print(nums[i]+" ");
        }
    }
    public static int getMiddle(int[] nums,int left,int right){
        int i=left,j=right;
        int key=nums[left];
        while(i<j){
            while(nums[j]>=key&&i<j)
                j--;
            nums[i]=nums[j];
            while(nums[i]<=key&&i<j)
                i++;
            nums[j]=nums[i];
        }
        nums[i]=key;
        return i; 
    }
    public static void quickSort(int[] nums,int low ,int high){
        if(low<high){
            int middle = getMiddle(nums, low, high);
            quickSort(nums, low, middle-1);
            quickSort(nums, middle+1, high);
        }
    }

    /**
     * 穩定，O(nlogn)
     */
    public static void mergeSort(int[] nums){
        int[] temp = new int[nums.length];
        mergeSort(nums, 0, nums.length-1, temp);
        System.out.println("\n"+"merge:");
        for(int i=0;i<nums.length;i++){
            System.out.print(nums[i]+" ");
        }
        
    }
    public static void mergeSort(int[] arr,int left,int right,int[] temp) {
        if(left<right){
            int mid=(left+right)/2;
            mergeSort(arr, left, mid, temp);
            mergeSort(arr, mid+1, right, temp);
            merge(arr, left, mid, right, temp);
        }
    }
    public static void merge(int[] arr, int left, int mid, int right, int[] temp){
        int i=left;
        int j=mid+1;
        int t=0;
        while(i<=mid&&j<=right){
            if(arr[i]<=arr[j]){
                temp[t++]=arr[i++];
            }else{
                temp[t++]=arr[j++];
            }
        }
        while(i<=mid){
            temp[t++] = arr[i++];
        }
        while(j<=right){
            temp[t++] = arr[j++];
        }
        t=0;
        while(left<=right){
            arr[left++]=temp[t++];
        }
    }

    public static int binSearch(int[] nums,int low,int high,int key){
        if(low<=high){
            int mid = low+(high-low)/2;
            if(nums[mid]==key){
                return mid;
            }else if(nums[mid]>key){
                return binSearch(nums, low, mid-1, key);
            }else{
                return binSearch(nums, mid+1, high, key);
            }
        }
        return -1;
    }

    public static int commonBinSerach(int[] nums,int key){
        int low = 0;
        int high = nums.length-1;
        int middle = 0;
        while(low<=high){
            middle=(low+high)/2;
            if(nums[middle]>key){
                high=middle-1;
            }else if(nums[middle]<key){
                low=middle+1;
            }else{
                return middle;
            }
        }
        return -1;
    }

    public static void main(String[] args) {
        int[] nums = {4,5,9,8,7,3,6,1,2,0};
        System.out.println("\n"+"original:");
        for(int i=0;i<nums.length;i++){
            System.out.print(nums[i]+" ");
        }
        System.out.println("\n");
        //bubbleSort(nums);
        //selectSort(nums);
        //insertSort(nums);
        //shellSort(nums);        
        //quickSort(nums);
        //mergeSort(nums);

        System.out.println("\nplease input a num of array:");
        Scanner input = new Scanner(System.in);
        int x = input.nextInt();
        System.out.println("position: "+commonBinSerach(nums,x));
        System.out.println("the position of "+x+" is: "+binSearch(nums, 0, nums.length-1, x));
        input.close();
        
    }
}