Java | 10种排序算法

冒泡排序

    public void sort(int[] a) {
        for(int i=0;i a[j+1]){
                    int temp = a[j];
                    a[j] = a[j+1];
                    a[j+1] = temp;
                    flag = false;
                }
            }
            if(flag)
                break;
        }
    }

选择排序

    public void sort(int[] a) {
        for(int i=0;i a[j])
                    index = j;
            }
            if(index > i){
                int temp = a[index];
                a[index] = a[i];
                a[i] = temp;
            }
        }
    }

插入排序

    public void sort(int[] a) {
        for(int i=1;i=0 && temp

希尔排序

    public void sort(int[] a) {
        for(int g=a.length/2;g>=1;g/=2){  // 缩小增量
            for(int i=g;i=0 && temp

计数排序

    public void sort(int[] a) {
        int[] b= new int[a.length];
        int max = a[0], min = a[0];
        for (int i : a) {
            max = Math.max(max, i);
            min = Math.min(min, i);
        }
        int k = max - min + 1;
        int[] c = new int[k];

        for (int i = 0; i < a.length; ++i) {
            c[a[i] - min] += 1;
        }

        for (int i = 1; i < c.length; ++i) {  // 保存元素位置
            c[i] = c[i] + c[i - 1];
        }

        for (int i = a.length - 1; i >= 0; --i) {  // 从后往前遍历，保证稳定排序
            b[--c[a[i] - min]] = a[i];
        }

        System.arraycopy(b, 0, a, 0, a.length);
    }

基数排序

    public void sort(int[] a, int digit) {
        double max = Math.pow(10, digit);
        for (int exp = 1; exp < max; exp *= 10) {
            int[] temp = new int[a.length];
            int[] buckets = new int[10];

            for (int value : a) {
                buckets[(value / exp) % 10]++;
            }

            for (int i = 1; i < 10; i++) {
                buckets[i] += buckets[i - 1];
            }

            for (int i = a.length - 1; i >= 0; i--) {
                temp[--buckets[(a[i] / exp) % 10]] = a[i];
            }

            System.arraycopy(temp, 0, a, 0, a.length);
        }
    }

堆排序

    private void heapify(int[] a, int i, int n){
        while(2*i+1 < n){
            int j = 2*i+1;
            if(j+1 < n && a[j] < a[j+1]) j++;
            if(a[i] < a[j]){
                int temp = a[i];
                a[i] = a[j];
                a[j] = temp;
                i = j;
            }
            else
                break;
        }
    }

    public void sort(int[] a) {
        int n = a.length;
        for(int i=n/2-1;i>=0;i--){
            heapify(a, i ,n);
        }

        for(int i=n-1;i>0;i--){
            int temp = a[0];
            a[0] = a[i];
            a[i] = temp;
            heapify(a, 0, i);
        }
    }

归并排序

    public void sort(int[] a) {
        mergeSort(a, 0, a.length - 1);
    }

    private void mergeSort(int[] a, int left, int right) {
        if(left >= right) {
            return;
        }
        int mid = left + ((right - left) >> 1);
        mergeSort(a, left, mid);
        mergeSort(a, mid + 1, right);
        merge(a, left, mid, right);
    }

    private void merge(int[] a, int left, int mid, int right) {
        int[] temp = new int[right - left + 1];
        int i = 0;
        int p1 = left;
        int p2 = mid + 1;

        while(p1 <= mid && p2 <= right) {
            temp[i++] = a[p1] <= a[p2] ? a[p1++] : a[p2++];
        }
        while(p1 <= mid) {
            temp[i++] = a[p1++];
        }
        while(p2 <= right) {
            temp[i++] = a[p2++];
        }

        for(i = 0; i < temp.length; i++) {
            a[left + i] = temp[i];
        }
    }

快速排序

    public void sort(int[] a) {
        quickSort(a, 0, a.length - 1);
    }

    private void quickSort(int[] a, int i, int j) {
        if (i < j) {
            int q = partition(a, i, j);
            quickSort(a, i, q-1);
            quickSort(a, q+1, j);
        }
    }

    private int partition(int[] a, int i, int j) {
        int left = i;
        int right = j;
        int pivot = a[i];
        while (left <= right) {
            while (left <= right && a[left] <= pivot) left++;
            while (left <= right && a[right] > pivot) right--;
            if (left < right) {
                int temp = a[left];
                a[left] = a[right];
                a[right] = temp;
            }
        }
        a[i] = a[right];
        a[right] = pivot;

        return right;
    }

桶排序

    public void sort(int[] a) {
        int max = a[0], min = a[0];
        for (int i = 0; i < a.length; i++) {
            max = Math.max(max, a[i]);
            min = Math.min(min, a[i]);
        }

        int bucketNum = (max - min) / a.length + 1;
        ArrayList> bucketArr = new ArrayList<>(bucketNum);
        for (int i = 0; i < bucketNum; i++) {
            bucketArr.add(new ArrayList<>());
        }

        for (int i = 0; i < a.length; i++) {
            int num = (a[i] - min) / a.length;
            bucketArr.get(num).add(a[i]);
        }

        for (int i = 0; i < bucketArr.size(); i++) {
            Collections.sort(bucketArr.get(i));
        }

        int k = 0;
        for (int i = 0; i < bucketArr.size(); i++) {
            for (int j = 0; j < bucketArr.get(i).size(); j++) {
                a[k++] = bucketArr.get(i).get(j);
            }
        }
    }