归并排序 C++实现

归并排序是众多排序算法中的一种，它采用分治递归的方法，时间复杂度为O(nlogn),空间复杂度为O(n)。

基本思想是首先将整个区间分成两部分，分别对其进行求解，再对这两部分再次分解，直到区间分得足够小的时候进行计算，最终再合并。

#include <cstdio>#include <cstring>using namespace std;void Merge(int *arry, int left, int mid, int right){    int len1 = mid - left + 1;    int len2 = right - mid;    int *arry1 = new int[len1];    int *arry2 = new int[len2];    for(int i = 0; i < len1; i++)        arry1[i] = arry[left + i];    for(int i = 0; i < len2; i++)        arry2[i] = arry[mid + 1 + i];    int ind = left, ind1 = 0, ind2 = 0;    while(ind1 < len1 && ind2 < len2){        if(arry1[ind1] <= arry2[ind2])            arry[ind++] = arry1[ind1++];        else            arry[ind++] = arry2[ind2++];    }    while(ind1 < len1)        arry[ind++] = arry1[ind1++];    while(ind2 < len2)        arry[ind++] = arry2[ind2++];    delete[] arry1;    delete[] arry2;}void Merge_Sort(int *arry, int left, int right){    if(right - left < 1)        return;    int mid = (left + right) / 2;    Merge_Sort(arry, left, mid);    Merge_Sort(arry, mid + 1, right);    Merge(arry, left, mid, right);}int main(){    int a[] = {4, 3, 9, 10, -9, 8, 33};    int len = sizeof(a) / sizeof(int);    Merge_Sort(a, 0, len - 1);    for(int i = 0; i < len; i++)        printf("%d ", a[i]);    printf("\n");    return 0;}