AcWing 787. 归并排序

Posted 2021-05-20 幽殇默

https://www.acwing.com/problem/content/description/789/

#include<cstdio>
using namespace std;
const int N=100010;
int a[N];
int tmp[N];
void merge_sort(int q[],int l,int r)
{
    if(l>=r) return;//说明已经分成一个一个的了
    int mid=l+r>>1;
    merge_sort(q,l,mid),merge_sort(q,mid+1,r);

    int k=0;
    int i=l;//左区间的头 
    int j=mid+1; //右区间的头
    while(i<=mid&&j<=r)
    {
        if(q[i]<=q[j]) tmp[k++]=q[i++];
        else tmp[k++]=q[j++];
    } 
    while(i<=mid) tmp[k++]=q[i++];
    while(j<=r) tmp[k++]=q[j++];
    for(i=l,j=0;i<=r;i++,j++) q[i]=tmp[j];
}
int main(void)
{
    int n; scanf("%d",&n);
    for(int i=0;i<n;i++) scanf("%d",&a[i]);
    merge_sort(a,0,n-1);
    for(int i=0;i<n;i++) printf("%d ",a[i]);
    puts("");
    return 0;
}