MergeSort 归并排序

实现：

二路归并

public class TestMergeSort {

    

    public int[] mergeSortArray(int[] arr, int left, int right){

        if(left >= right) return null;

        

        int mid = (left+right)/2;

        mergeSortArray(arr, left, mid);

        mergeSortArray(arr, mid+1, right);

        

        merge(arr, left, mid, right);

        return arr;

    }

    

    public int[] merge(int[] arr, int left, int mid,  int right){

        int[] temp = new int[arr.length];

        int r1 = mid +1;

        int tIndex = left;

        int cIndex = left;

        

        while(left<=mid && r1<=right){

            if(arr[left] <= arr[r1]){

                temp[tIndex++] = arr[left++];

            }else{

                temp[tIndex++] = arr[r1++];

            }

        }

        

        while(left <= mid){

            temp[tIndex++] = arr[left++];

        }

        

        while(r1<=right){

            temp[tIndex++] = arr[r1++];

        }

        

        while(cIndex <= right){

            arr[cIndex] = temp[cIndex];

            cIndex++;

        }

        

        return arr;

    }

    

    

    public static void main(String[] args) {

        int[] arr = {6,2,4,1,5,9};

        TestMergeSort test = new TestMergeSort();

        test.mergeSortArray(arr, 0, arr.length -1);

        

        for(int i = 0 ; i < arr.length; i ++){

            System.out.println(arr[i]);

        }

    }



}

 

这个哥哥讲的不错，跟他学习了：

http://www.cnblogs.com/shudonghe/archive/2013/09/05/3302888.html

 

这个可以看看：

http://www.cnblogs.com/luweiseu/archive/2012/07/14/2591653.html