Submission #4260907

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Source Code Expand

#include<cstdio>
#include<cctype>
#include<algorithm>
using namespace std;
const int N=1e5+5;
inline int read(){
	int x=0,w=0;char ch=0;
	while(!isdigit(ch)) w|=ch=='-',ch=getchar();
	while(isdigit(ch)) x=(x<<1)+(x<<3)+(ch^48),ch=getchar();
	return w?-x:x;
}
struct Node{
	int data,id;
	inline bool operator <(const Node &x)const{return data<x.data;}
}a[N];
int n,ans,b[N];
int main(){
	freopen("F.in","r",stdin);
	n=read();
	for(int i=1;i<=n;++i) a[i].data=read(),a[i].id=i;
//	bool fg=0;
//	for(int t=1;t<=500000;++t){
//		fg=0;
//		for(int i=2;i<=n-1;++i)
//		 	if(a[i-1].data>a[i+1].data){
//		 		swap(a[i-1].data,a[i+1].data);	
//		 		fg=1;
//			 }
//		if(!fg) break;
//	}
//	//for(int i=1;i<=n;++i) printf("%d ",a[i]);
//	//puts("");
//	for(int i=n;i>=2;--i){
//		fg=0;
//		for(int j=1;j<=i-1;++j)
//			if(a[j].data>a[j+1].data){
//				swap(a[j].data,a[j+1].data);++ans;
//				fg=1;
//			}
//		if(!fg) break;
//	}
	sort(a+1,a+n+1);
	for(int i=1;i<=n;++i) b[a[i].id]=i;
	for(int i=1;i<=n;++i) if((a[i].id&1)!=(i&1)){
		++ans;
		++a[b[i]].id;
		//b[i+1]=b[i];
	}
	printf("%d\n",ans);
	return 0;
}

Submission Info

Compile Error

./Main.cpp: In function ‘int main()’:
./Main.cpp:18:27: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result]
  freopen("F.in","r",stdin);
                           ^

Judge Result