归并排序

    归并排序：将两个或者两个以上的额有序表合并成一个新表。它的每一趟时间复杂度是O(n)，需要O(log2n)趟（n个元素，利用2路归并排序）。所以时间复杂度是O(nlog2n)

public class Solution1 {

      publicstatic void Merge(int nums[],int low,int mid,int high){

           //两个表low,mid mid+1,high合并

           intnums1[]=new int[nums.length];

           for(inti=low;i<=high;i++){

                 nums1[i]=nums[i];

           }

           intj,k,i;

           for(i=low,j=mid+1,k=i;i<=mid&&j<=high;k++){//比较B的左右字段，将较小的复制到A中

                 if(nums1[i]<=nums[j])

                      nums[k]=nums1[i++];

                 else

                      nums[k]=nums1[j++];

                

           }

           while(i<=mid)nums[k++]=nums1[i++];

           while(j<=high)nums[k++]=nums1[j++];

      }

      publicstatic void MergeSort(int nums[],int low,int high){

           if(low<high){

                 intmid=(low+high)/2;

                 MergeSort(nums,low,mid);//左侧进行递归

                 MergeSort(nums,mid+1,high);//右侧进行递归

                 Merge(nums,low,mid,high);//合并

           }

      }

      publicstatic void main(String[] args) {

           intnums[]=new int[]{53,17,78,9,45,65,87,32};

           MergeSort(nums,0,nums.length-1);

           System.out.println(Arrays.toString(nums));

      }

 }