Acwing787.归并排序

Acwing787.归并排序

归并模板

归并排序，合二为一

题目链接：Acwing787.归并排序

#include<iostream>
using namespace std;

const int N =1e6+10;

int n ;
int q[N],temp[N];

void merge_sort(int q[],int l ,int r )
{
    if(l >=r)return ;

    int mid =l+r >>1;

    merge_sort(q,l,mid),merge_sort(q,mid+1,r);

    int k = 0 , i = l , j = mid +1 ;
    while( i <= mid && j <= r)
        if(q[i]<=q[j])temp[k++]=q[i++];
        else temp[k++]=q[j++];
    while(i<=mid)temp[k++]=q[i++];
    while(j<=r)temp[k++]=q[j++];

        for(i = l ,j=0;i<=r ;i++,j++)q[i]=temp[j];
}

int main()
{
    scanf("%d",&n);
    for(int i = 0 ;i <n ;i++)scanf("%d",&q[i]);

    merge_sort(q, 0  , n-1);

    for(int i=0;i<n;i++)printf("%d ",q[i]);
}

练习题：Acwing788.逆序对的数量

欠着。晚点补。