【算法题】归并排序

参考的剑指offer题36：
http://blog.csdn.net/xiaxzhou/article/details/74347863

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#include <algorithm>#include <numeric>#include <vector>using namespace std;void merge(vector<int>& array,vector<int>& array_copy, int left, int k, int right){    if (array.empty()||array_copy.empty()||left>=right)    {        return;    }    int index(left);    int left_index(left), right_index(k + 1);    while (left_index <= k&&right_index <= right)    {        if (array_copy[left_index]<array_copy[right_index])        {            array[index++] = array_copy[left_index++];        }        else        {            array[index++] = array_copy[right_index++];        }    }    while (left_index <= k)    {        array[index++] = array_copy[left_index++];    }    while (right_index<= right)    {        array[index++] = array_copy[right_index++];    }}void merge_sort_core(vector<int>&  array, vector<int>&  array_copy, int left, int right){    if (array.empty()||array_copy.empty()||left>=right)    {        return;    }    int k = left + ((right - left) >> 1);    merge_sort_core(array_copy, array, left, k);    merge_sort_core(array_copy, array, k+1, right);    merge(array, array_copy, left, k, right);}void merge_sort(vector<int>& array, int len){    if (array.empty()||len<2)    {        return;    }    int left(0), right(len - 1);    vector<int> array_copy (array);    merge_sort_core(array, array_copy, left, right);}void main(){    vector<int> array{3, 1, 2, 5, 8, 7, 6, 4};    merge_sort(array, 8);    return;}