排序算法

时间复杂度

冒泡排序

public class bubbleSort {
    public static void println(int[] num){
        for(int i=0;i<num.length;i++){
            System.out.println(num[i]);
        }
    }

    public static void bubbleSort(int[] num){
        for(int i=0;i<num.length;i++){
            for(int j=0;j<num.length-i-1;j++){
                if(num[j]>num[j+1]){
                    int tmp=num[j];
                    num[j]=num[j+1];
                    num[j+1]=tmp;
                }
            }
        }
        println(num);
    }
    public static void main(String[] args){
        int num[]={10,9,8,7,6,5,4,3,2,1};
        bubbleSort(num);
    }
}

选择排序

public class selectSort {
    public static void println(int[] num){
        for(int i=0;i<num.length;i++){
            System.out.println(num[i]);
        }
    }
    public static void selectionSort(int[] num){
        if(num.length!=0){
            for(int i=0;i< num.length;i++){
                int mark=i;
                for(int j=i;j< num.length;j++){
                    if(num[mark]>num[j]){
                        mark=j;
                    }
                }
                int tmp=num[i];
                num[i]=num[mark];
                num[mark]=tmp;
            }
        }
        println(num);
    }
    public static void main(String[] args){
        int num[]={10,9,8,7,6,5,4,3,2,1};
        selectionSort(num);
    }
}

插入排序

public class insertionSort {
    public static void println(int[] num){
        for(int i=0;i<num.length;i++){
            System.out.println(num[i]);
        }
    }

    public static void insertionSort(int[] num) {
        if (num.length != 0) {
            int current;
            for (int i = 0; i < num.length - 1; i++) {
                current = num[i + 1];
                int preIndex = i;
                while (preIndex >= 0 && current < num[preIndex]) {
                    num[preIndex + 1] = num[preIndex];
                    preIndex--;
                }
                num[preIndex + 1] = current;
            }
        }
        println(num);
    }

    public static void main(String[] args){
        int num[]={10,9,8,7,6,5,4,3,2,1};
        insertionSort(num);
    }
}

希尔排序

public class shellSort {
    public static void println(int[] num){
        for(int i=0;i<num.length;i++){
            System.out.println(num[i]);
        }
    }

    public static void shellSort(int[] num){
        int len= num.length;
        int tmp,gap=len/2;
        while(gap>0){
            for(int i=gap;i<len;i++){
                tmp=num[i];
                int preIndex=i-gap;
                while(preIndex>=0&&num[preIndex]>tmp){
                    num[preIndex+gap]=num[preIndex];
                    preIndex=preIndex-gap;
                }
                num[preIndex+gap]=tmp;
            }
            //缩小增量
            gap=gap/2;
        }
        println(num);
    }

    public static void main(String[] args){
        int num[]={10,9,8,7,6,5,4,3,2,1,13,12,11};
        shellSort(num);
    }
}

归并排序

public class mergeSort {
    public static void main(String []args){
        int []arr = {10,9,8,7,6,5,4,3,2,1};
        sort(arr);
        for(int i=0;i<arr.length;i++){
            System.out.println(arr[i]);
        }
    }
    public static void sort(int []arr){
        int []temp = new int[arr.length];//在排序前，先建好一个长度等于原数组长度的临时数组，避免递归中频繁开辟空间
        sort(arr,0,arr.length-1,temp);
    }

    public static void sort(int[] arr,int left,int right,int []temp){
        if(left<right){
            int mid = (left+right)/2;
            sort(arr,left,mid,temp);//左边归并排序，使得左子序列有序
            sort(arr,mid+1,right,temp);//右边归并排序，使得右子序列有序
            merge(arr,left,mid,right,temp);//将两个有序子数组合并操作
        }
    }
    public static void merge(int[] arr,int left,int mid,int right,int[] temp){
        int i = left;//左序列指针
        int j = mid+1;//右序列指针
        int t = 0;//临时数组指针
        while (i<=mid && j<=right){
            if(arr[i]<=arr[j]){
                temp[t++] = arr[i++];
            }else {
                temp[t++] = arr[j++];
            }
        }
        while(i<=mid){//将左边剩余元素填充进temp中
            temp[t++] = arr[i++];
        }
        while(j<=right){//将右序列剩余元素填充进temp中
            temp[t++] = arr[j++];
        }
        t = 0;
        //将temp中的元素全部拷贝到原数组中
        while(left <= right){
            arr[left++] = temp[t++];
        }
    }
}

快速排序

public class quickSort {
    public static void println(int[] num){
        for(int i=0;i<num.length;i++){
            System.out.println(num[i]);
        }
    }
    //快速排序
    public static void quick_sort(int s[], int l, int r) {
        if (l < r) {
            int i = l, j = r, x = s[l];
            while (i < j) {
                while(i < j && s[j] >= x) {
                    // 从右向左找第一个小于x的数
                    j--;
                }
                if(i < j){
                    s[i++] = s[j];
                }
                while(i < j && s[i] < x){
                    // 从左向右找第一个大于等于x的数
                    i++;
                }
                if(i < j){
                    s[j--] = s[i];
                }
            }
            s[i] = x;
            quick_sort(s, l, i - 1); // 递归调用
            quick_sort(s, i + 1, r);
        }
    }
    public static void main(String[] args){
        int[] num={10,9,8,7,6,5,4,3,2,1};
        quick_sort(num,0,9);
        println(num);
    }
}

堆排序

public class heapSort {
    static int len;
    public static void swap(int[] num,int left,int right){
        int tmp=num[left];
        num[left]=num[right];
        num[right]=tmp;
    }
    public static int[] heapSort(int[] num){
        len=num.length;
        if(len<1){
            return num;
        }
        //构建一个最大堆
        buildMaxHeap(num);
        //循环将首位与末末位交换然后再重新调整最大堆
        while(len>0){
            swap(num,0,len-1);
            len--;
            adjustHeap(num,0);
        }
        return num;
    }
    public static void buildMaxHeap(int[] num){
        for(int i=(len/2-1);i>=0;i--){
            adjustHeap(num,i);
        }
    }
    public static void adjustHeap(int[] num,int i){
        int maxIndex=i;
        //如果有左子树，且左子树大于父节点，则将最大值真指向左子树
        if(i*2+1<len&&num[i*2]>num[maxIndex]){
            maxIndex=i*2;
        }
        //如果有右子树且右子树大于父节点，则将最大指针指向右子树
        if(i*2+1<len&&num[i*2+1]>num[maxIndex]){
            maxIndex=i*2+1;
        }
        if(maxIndex!=i){
            swap(num,maxIndex,i);
            adjustHeap(num,maxIndex);
        }
    }
    public static void main(String[] args){
        int[] num={10,9,8,7,6,5,4,3,2,111};
        heapSort(num);
        for(int i=0;i< num.length;i++){
            System.out.println(num[i]);
        }
    }
}