Submission #950022

#	Time	Username	Problem	Language	Result	Execution time	Memory
950022		vjudge1	Vudu (COCI15_vudu)	C++17	140 / 140	559 ms	49960 KiB

vudu

#include <bits/stdc++.h>
 
#define ff first
#define ss second
#define pb push_back
#define all(x) x.begin(),x.end()
#define rall(x) x.rbegin(),x.rend()
#define int long long
#define rnd(l, r) uniform_int_distribution<int>(l, r)(rng)
 
using namespace std;

void fp(string name){freopen((name+".in").c_str(),"r",stdin); freopen((name+".out").c_str(),"w",stdout);} 
int pow(int a,int b,int m){int ans=1;while(b){if(b&1){ans=(ans*a)%m;}b>>=1;a=(a*a)%m;}return ans;}
int binpow(int a,int b){int ans=1;while(b){if(b&1){ans=(ans*a);}b>>=1;a=(a*a);}return ans;}
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
 
const int N = 1e6 + 10, MX = 1e6 + 1;

int a[N], pref[N], t[N * 4];
vector <int> indices = {0};

int getCompressedIndex(int a) {
	return lower_bound(indices.begin(), indices.end(), a) - indices.begin();
}

void update(int pos, int x, int v = 1,int tl = 0, int tr = MX){
    if(tl == tr){
        t[v] += x;
    }else{
        int mid = (tl + tr) >> 1;
        if(pos <= mid)
			update(pos, x, v * 2, tl, mid);
        else
			update(pos, x, v * 2 + 1,mid + 1, tr);
        t[v] = (t[v * 2] + t[v * 2 + 1]);
    }
}
 
int get(int l, int r, int v = 1, int tl = 0, int tr = MX){
    if(tl > r || tr < l)
        return 0;
    if(tl >= l && tr <= r){
        return t[v];
    }
    int mid = (tl + tr) >> 1;
    return (get(l, r, v * 2, tl, mid) + get(l, r, v * 2 + 1, mid + 1, tr));
}

main(){
	iostream::sync_with_stdio(false);	
    cin.tie(nullptr);
    cout.tie(nullptr);
	int n;
	cin >> n;
	for(int i = 1; i <= n; i++){
		cin >> a[i];
	}
	
	int P;
	cin >> P;
	for(int i = 1; i <= n; i++){
		a[i] -= P;
		pref[i] = a[i] + pref[i - 1];
		indices.pb(pref[i]);
	}
	int ans = 0;
	sort(indices.begin(), indices.end());
	indices.erase(unique(indices.begin(), indices.end()), indices.end());
	for(int i = n; i >= 0; i--){
		int x = getCompressedIndex(pref[i]);
		ans += get(x, n + 1);
		update(x, 1);
	}
	cout << ans << endl;
}	
/*
 * Before implementing the problem:
	
	Do I understand the problem correctly?
	Which places are tricky? What do I need to remember to implement them correctly?
	Which place is the heaviest by implementation? Can I do it simpler?
	Which place is the slowest? Where do I need to be careful about constant factors and where I can choose slower but simpler implementation?
	----------------------------------
	If not AC:
 
	Did you remember to do everything to handle the tricky places you thought about before?
	Is the solution correct?
	Do I understand the problem correctly?
	----------------------------------
	If you have a test on which the solution gives wrong answer:
 
	Is the solution doing what it was supposed to do?
	Is the problem in the code or in the idea?
*/

Compilation message (stderr)

vudu.cpp:50:1: warning: ISO C++ forbids declaration of 'main' with no type [-Wreturn-type]
   50 | main(){
      | ^~~~
vudu.cpp: In function 'void fp(std::string)':
vudu.cpp:13:29: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   13 | void fp(string name){freopen((name+".in").c_str(),"r",stdin); freopen((name+".out").c_str(),"w",stdout);}
      |                      ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
vudu.cpp:13:70: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   13 | void fp(string name){freopen((name+".in").c_str(),"r",stdin); freopen((name+".out").c_str(),"w",stdout);}
      |                                                               ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

• Subtask 1: 140 / 140