Submission #1272050

#	Time	Username	Problem	Language	Result	Execution time	Memory
1272050		herominhsteve	Fire (BOI24_fire)	C++20	100 / 100	120 ms	41336 KiB

Main

#include<bits/stdc++.h>
#define el '\n'
#define FNAME "CAMERA"
#define allof(x) x.begin(),x.end()
#define allof1(x) x.begin()+1,x.end()
#define mset(x,n) memset((x),(n),sizeof(x));
using namespace std;
const long long MOD = (long long) 1e9+7;
template<class X,class Y> bool minimize(X &a,Y b){if (a>b){a=b; return true;} return false;}
template<class X,class Y> bool maximize(X &a,Y b){if (a<b){a=b; return true;} return false;}

void setup(){
    ios_base::sync_with_stdio(0);
    cin.tie(0);cout.tie(0);
    if (fopen(FNAME".inp","r")){
        freopen(FNAME".inp","r",stdin);
        freopen(FNAME".out","w",stdout);
    }
}

const int MAXN = 4e5 + 5;
const int LOG = 20;
const int INF = (int) 1e9 + 15092007;

int n,m;
long long s[MAXN],e[MAXN];
// ? ID of the next nearest jumpable
int nxt[MAXN];
int up[LOG+1][MAXN];

void init(){
	cin>>n>>m;
	for (int i=0;i<n;i++) cin>>s[i]>>e[i];
}

void removeUseless(){
	vector<pair<long long,long long>> shift;
	for (int i=0;i<n;i++){
		shift.emplace_back(s[i],e[i]);
	}
	sort(allof(shift),[](const pair<long long,long long> &a,const pair<long long,long long> &b){
		return (a.first<b.first or (a.first==b.first and a.second>b.second));
	});

	int newN=0;
	long long maxE=-1;
	for (pair<long long,long long> p : shift){
		long long start,end; tie(start,end) = p;
		if (maximize(maxE,end)){
			s[newN] = start;
			e[newN] = end;
			newN++;
		}
	}
	n = newN;
}

void modify(){
	for (int i=0;i<n;i++) if (s[i] > e[i]) e[i] += m;
	for (int i=0;i<n;i++){
		s[i + n] = s[i] + m;
		e[i + n] = e[i] + m;
	}
	n *= 2;
	removeUseless();
}

void calNxt(){
	vector<pair<long long,int>> cam;
	for (int i=0;i<n;i++) cam.emplace_back(s[i],i);
	sort(allof(cam));
	int r = 0;
	for (pair<long long,int> x : cam){
		int curID = x.second;
		while (r < n){
			int nxtID = cam[r].second;
			if (s[nxtID] > e[curID]) break;
			r++;
		}
		nxt[curID] = cam[r-1].second;
	}
}

void calUp(){
	for (int i=0;i<n;i++) up[0][i] = nxt[i];
	for (int k=1;k<=LOG;k++){
		for (int i=0;i<n;i++){
			up[k][i] = up[k-1][up[k-1][i]];
		}
	}
}

int getRes(int fCam){
	int cnt = 1;
	long long startTime = s[fCam];
	int u = fCam;

	for (int k=LOG;k>=0;k--){
		if (e[up[k][u]] < (startTime + m)){
			u = up[k][u];
			cnt += (1<<k);
		}
	}

	cnt++;
	u = up[0][u];

	if (e[u] < (startTime + m)) return INF;
	return cnt;
}

void sol(){
	modify();
	calNxt();
	calUp();

	int res = INF;
	for (int i=0;i<n;i++) minimize(res,getRes(i));

	cout<<(res==INF ? -1 : res);
}

int main(){
    setup();
    init();
    sol();
}

Compilation message (stderr)

Main.cpp: In function 'void setup()':
Main.cpp:16:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   16 |         freopen(FNAME".inp","r",stdin);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~
Main.cpp:17:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   17 |         freopen(FNAME".out","w",stdout);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~

• Subtask 1: 14 / 14
• Subtask 2: 17 / 17
• Subtask 3: 9 / 9
• Subtask 4: 13 / 13
• Subtask 5: 21 / 21
• Subtask 6: 26 / 26