#include<stdio.h>
//合并两个有序数组
#define N 1000005
int a[N],c[N];
int count=0;//先定义count
void merge(int left,int right){
int mid;
mid=(left+right)/2;
int i=left;
int j=mid+1;
int k=left;
while(i<=mid &&j<=right ){
if(a[i]<=a[j]){
c[k++]=a[i++];
}else{
c[k++]=a[j++];
count+=mid-i+1;
}
}
while(i<=mid){
c[k++]=a[i++];
}while(j<=right){
c[k++]=a[j++];
}
for(int m=left;m<=right;m++){
a[m++]=c[m++];
}
}
//将一个乱序数组排好序(条件是left<right)
void mergesort(int left,int right){
if(left<right){
int mid=(left+right)/2;
mergesort(left,mid);
mergesort(mid+1,right);
merge(left,right);
}
}
int main(){
int n;
scanf("%d",&n);
for(int i=0;i<n;i++){
scanf("%d",&a[i]);
}
mergesort(0,n-1);
printf("%d",count);
}
DEV是 11
但是c语言网那个编程网站是14