归并排序

来源：互联网发布：linux环境搭建编辑：程序博客网时间：2024/04/29 16:34

如果归并排序中待归并的两个相邻序列分别Wi是r[start]~r[mid]和r[mid+1]~r[end]，需要将其归并成一个新序列r1[start]~r1[end]：

void merge(int r[], int r1[], int start, int mid, int end){    int i = start, j = mid + 1, k = start;    while (i <= mid && j <= end)        r1[k++] = (r[i] < r[j] ? r[i++] : r[j++]);    memcpy(r1 + k, r + i, (mid - i + 1) * sizeof(int)); k += mid - i + 1;    memcpy(r1 + k, r + j, (end - j + 1) * sizeof(int)); k += end - j + 1;}

一趟归并排序：

void MergePass(int r[], int r1[], int n, int h){    int i = 1;    while (i < n - h * 2 + 1)    {        merge(r, r1, i , i + h - 1, i + h * 2 - 1);        i += (h * 2);    }    if (i < n - h + 1) merge(r, r1, i, i + h - 1, n);    else memcpy(r1 + i, r + i, (n - i + 1) * sizeof(int));}

归并排序主函数：

void MergeSort(int r[], int n){    int *r1 = new int [n + 1];    int h = 1;    while (h < n)    {        MergePass(r, r1, n, h);        h <<= 1;        if (h >= n)        {            memcpy(r, r1, (n + 1) * sizeof(int));            break;        }        MergePass(r1, r, n, h);        h <<= 1;    }    delete r1[];}

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