归并排序的递归与非递归实现Java

 public static int[] sort(int[] nums, int low, int high) {  
        int mid = (low + high) / 2;  
        if (low < high) {  
            // 左边  
            sort(nums, low, mid);  
            // 右边  
            sort(nums, mid + 1, high);  
            // 左右归并  
            merge(nums, low, mid, high);  
        }  
        return nums;  
    }  
  
    public static void merge(int[] nums, int low, int mid, int high) {  
        int[] temp = new int[high - low + 1];  
        int i = low;// 左指针  
        int j = mid + 1;// 右指针  
        int k = 0;  
  
        // 把较小的数先移到新数组中  
        while (i <= mid && j <= high) {  
            if (nums[i] < nums[j]) {  
                temp[k++] = nums[i++];  
            } else {  
                temp[k++] = nums[j++];  
            }  
        }  
  
        // 把左边剩余的数移入数组  
        while (i <= mid) {  
            temp[k++] = nums[i++];  
        }  
  
        // 把右边边剩余的数移入数组  
        while (j <= high) {  
            temp[k++] = nums[j++];  
        }  
  
        // 把新数组中的数覆盖nums数组  
        for (int k2 = 0; k2 < temp.length; k2++) {  
            nums[k2 + low] = temp[k2];  
        }  
    }  

非递归实现

public static int[] sort(int[] nums, int low, int high) {  
       for(int i=low;i<=high;i*=2)
       {
    	   for(int j=low;j<=high-i;j+=2*i){
    		   merge(nums, j, j+i-1, Math.min(j+2*i-1, high));
    	   }
       }
        return nums;  
    }