归并排序mergeSort

废话不多说，直接show code:

#include<iostream>
using namespace std;

//归并过程
void merge(int *a, int start, int mid, int end){
    int *temp = new int[end - start + 1];
    int i = start;
    int j = mid + 1;
    int k = 0;
    while(i<=mid && j<=end){
        if(a[i] <= a[j]){
            temp[k++] = a[i++];
        }
        else{
            temp[k++] = a[j++];
        }
    }
    while(i <= mid){
        temp[k++] = a[i++];
    }
    while(j <= end){
        temp[k++] = a[j++];
    }
    for(i = 0; i < k; i++){
        a[start + i] = temp[i];
    }
    delete[] temp;
}

//递归过程
void mergeSort(int *a, int start, int end){
    if(a==nullptr || start>=end) return;
    int mid = (end + start) / 2;
    mergeSort(a, start, mid);
    mergeSort(a, mid+1, end);
    merge(a, start, mid, end);
}

int main(){
    int a[] = {2,5,1,6,0,3,7,9,4,8};
    int length = sizeof(a)/sizeof(a[0]);
    mergeSort(a, 0, length-1);
    for(int i = 0; i < length; i++){
        printf("%d ",a[i]);
    }
    printf("\n");
    return 0;
}