Submission #329178

#	Time	Username	Problem	Language	Result	Execution time	Memory
329178		oak	Mountains (NOI20_mountains)	C++14	100 / 100	561 ms	28780 KiB

Mountains

#include<bits/stdc++.h>
#define si 300000
using namespace std;
int fw[si+1];
long long arr[si+1],db[si+1],sum[si+1];
void upd(int po,int val){
	for(;po<=si;po+=(po&-po)){
		fw[po]+=val;
	}
}
int qry(int po){
	int ret = 0;
	for(;po>=1;po-=(po&-po)){
		ret += fw[po];
	}
	return ret;
}
int main(){
	int n,j,i;
	scanf("%d",&n);
	
	map<long long,int> mp;
	int rl[n];
	for(i=0;i<n;i++){
		scanf("%lld",&arr[i]);
		db[i] = arr[i];
	}
	sort(db,db+n);
	int co = 1;
	for(i=0;i<n;i++){
		if(mp.find(db[i]) != mp.end())continue;
		mp[db[i]] = co;
		co++;
	}
	for(i=0;i<n;i++){
		rl[i] = mp[arr[i]];
	}
	for(i=0;i<n;i++){
		sum[i] = qry(rl[i]-1);
		upd(rl[i],1);
	}
	long long ans = 0;
	memset(fw,0,sizeof fw);
	for(i=n-1;i>=0;i--){
		sum[i] *= qry(rl[i]-1);
		upd(rl[i],1);
		ans += sum[i]*1ll;
	}
	printf("%lld",ans);
}

Compilation message (stderr)

Mountains.cpp: In function 'int main()':
Mountains.cpp:19:8: warning: unused variable 'j' [-Wunused-variable]
   19 |  int n,j,i;
      |        ^
Mountains.cpp:20:7: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   20 |  scanf("%d",&n);
      |  ~~~~~^~~~~~~~~
Mountains.cpp:25:8: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   25 |   scanf("%lld",&arr[i]);
      |   ~~~~~^~~~~~~~~~~~~~~~

• Subtask 1: 2 / 2
• Subtask 2: 4 / 4
• Subtask 3: 9 / 9
• Subtask 4: 36 / 36
• Subtask 5: 28 / 28
• Subtask 6: 9 / 9
• Subtask 7: 12 / 12