数据结构-归并排序

#include <iostream>

using namespace std;

void Merge(int* a,int low,int mid,int high){
    int* a1 = new int[high-low+1];
    int k = 0;          //k为a1的下标
    int i = low,j = mid+1;
    while(i <= mid && j <= high){   //两个小数组扫描
        if(a[i] <= a[j]){
            a1[k] = a[i];
            k++;
            i++;
        }
        else{
            a1[k] = a[j];
            k++;
            j++;
        }
    }

    while(i <= mid){
        a1[k] = a[i];
        i++;
        k++;
    }

    while(j <= high){
        a1[k] = a[j];
        j++;
        k++;
    }

    for(int i=low,k=0;i<=high;i++,k++){  //一节一节拷贝回原数组
        a[i] = a1[k];
    }

    delete[] a1;
}

void MergePass(int* a,int ChildLength,int n){
    int i;
    for(i=0;i+2*ChildLength-1<n;i=i+2*ChildLength){ //归并ChildLength长的两相邻子表
        Merge(a,i,i+ChildLength-1,i+2*ChildLength-1);
    }
    if(i+ChildLength-1 < n){    //余下两个子表，后者长度小于ChildLength
        Merge(a,i,i+ChildLength-1,n-1);
    }
}

void MergeSort(int* a,int n){
    for(int i=1;i<n;i*=2){
        MergePass(a,i,n);
    }
}

int main(){
    int a[] = {5,1,2,4,8,7,6,9,3,0,7,6};
    int n = sizeof(a)/sizeof(*a);

    MergeSort(a,n);

    for(int i=0;i<n;i++){
        cout << a[i] << " ";
    }

    return 0;
}