第 3 节 快速排序（第 1 版代码）

参考代码 1：

class Solution {

    public int[] sortArray(int[] nums) {
        quickSort(nums, 0, nums.length - 1);
        return nums;
    }

    private void quickSort(int[] nums, int left, int right) {
        if (left >= right) {
            return;
        }

        int pivotIndex = partition(nums, left, right);
        quickSort(nums, left, pivotIndex - 1);
        quickSort(nums, pivotIndex + 1, right);
    }

    private int partition(int[] nums, int left, int right) {
        int pivot = nums[left];

        int j = left;
        // all in nums[left + 1..j] <= pivot
        // all in nums(j..i) > pivot
        for (int i = left + 1; i <= right; i++){
            if (nums[i] <= pivot) {
                j++;
                swap(nums, i, j);
            }
        }
        swap(nums, left, j);
        return j;
    }

    private void swap(int[] nums, int index1, int index2) {
        int temp = nums[index1];
        nums[index1] = nums[index2];
        nums[index2] = temp;
    }

}

修改定义。

参考代码 2：

class Solution {

    public int[] sortArray(int[] nums) {
        quickSort(nums, 0, nums.length - 1);
        return nums;
    }

    private void quickSort(int[] nums, int left, int right) {
        if (left >= right) {
            return;
        }

        int pivotIndex = partition(nums, left, right);
        quickSort(nums, left, pivotIndex - 1);
        quickSort(nums, pivotIndex + 1, right);
    }

    private int partition(int[] nums, int left, int right) {
        int pivot = nums[left];

        int j = left + 1;
        // all in nums[left + 1..j) <= pivot
        // all in nums[j..i) > pivot
        for (int i = left + 1; i <= right; i++){
            if (nums[i] <= pivot) {
                swap(nums, i, j);
                j++;
            }
        }
        swap(nums, left, j - 1);
        return j - 1;
    }

    private void swap(int[] nums, int index1, int index2) {
        int temp = nums[index1];
        nums[index1] = nums[index2];
        nums[index2] = temp;
    }

}

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作者：liweiwei1419 链接：https://suanfa8.com/quick-sort/quick-sort-basic 来源：算法吧 著作权归作者所有。商业转载请联系作者获得授权，非商业转载请注明出处。