java归并排序

public class Solution {
    public static void main(String[] args) {

    }

    public static void mergeSort(int[] nums) {
        int[] tmp = new int[nums.length];

        mergeSort(nums, tmp, 0, nums.length-1);
    }

    private static void mergeSort(int[] nums, int[] tmp, int left, int right) {
        if(left < right) {
            int mid = (left + right) >> 1;
            mergeSort(nums, tmp, left, mid);
            mergeSort(nums, tmp, mid+1, right);
            merge(nums, tmp, left, mid+1, right);
        }
    }

    private static void merge(int[] nums, int[] tmp, int leftPos, int rightPos, int rightEnd) {
        int leftEnd = rightPos-1;
        int tmpPos = leftPos;
        int numElements = rightEnd-leftPos+1;

        while(leftPos <= leftEnd && rightPos <= rightEnd) {
            if(nums[leftPos] <= nums[rightPos]) {
                tmp[tmpPos++] = nums[leftPos++];
            } else {
                tmp[tmpPos++] = nums[rightPos++];
            }
        }

        while(leftPos <= leftEnd) {
            tmp[tmpPos++] = nums[leftPos++];
        }

        while(rightPos <= rightEnd) {
            tmp[tmpPos++] = nums[rightPos++];
        }

        for(int i = 0; i < numElements; i++, rightEnd--) {
            nums[rightEnd] = tmp[rightEnd];
        }
    }
}