算法导论 分治法+归并排序的一种排序算法 C++实现

#include<iostream>
#include <time.h>
using namespace std;
void merge(int*A, int p, int q, int r)
{
    int i = 0;
    int index1 = 0;
    int index2 = 0;
    int length1 = q - p + 1;
    int length2 = r - q;
    int* arr1=new int[length1+1]; 
    int* arr2 = new int[length2+1];
    for (i = 0; i < length1; i++)
    {
        arr1[i] = A[p - 1 + i];
    }
    for ( i = 0; i < length2; i++)
    {
        arr2[i] = A[q + i];
    }
    arr1[length1] = 100;
    arr2[length2] = 100;

    for (i =p-1;i<=r-1;i++)
    {
        if (arr1[index1]<arr2[index2])
        {
            A[i] = arr1[index1];
            index1++;
        }
        else
        {
            A[i] = arr2[index2];
            index2++;
        }
    }
    delete[] arr1;
    delete[] arr2;
}
void merge_sort(int* A, int p, int r)
{
    int q;
    if (p<r)
    {
        q = (p + r) / 2;
        merge_sort(A, p, q);
        merge_sort(A, q + 1, r);
        merge(A, p, q, r);
    }
}

int main()
{
    srand((unsigned int)time(NULL));//设置当前时间为种子
    int p[20];
    for (size_t i = 0; i < 20; i++)
    {
        p[i] = rand() % 100 + 1;
    }
    merge_sort(p, 2, 17);
    for (size_t i = 1; i < 16; i++)
    {
        cout << p[i] << "\t";
    }
    system("pause");


}