Submission #133183

#	Time	Username	Problem	Language	Result	Execution time	Memory
133183		sealnot123	Mobile (BOI12_mobile)	C++14	15 / 100	352 ms	32728 KiB

mobile

#include<bits/stdc++.h>
#define x first
#define y second
#define pb push_back
#define eb emplace_back
#define all(a) (a).begin(),(a).end()
#define SZ(a) (int)(a).size()
using namespace std;
typedef long long LL;
typedef pair<LL,LL> PLL;
typedef pair<int,int> PII;
typedef double D;
typedef long double LD;
const int N = 1000007;
PLL tower[N];

bool cmp(PLL a, PLL b){
	if(a.x != b.x) return a.x > b.x;
	return a.y < b.y;
}

PLL intersect(PLL a, PLL b){
	LL A, B;
	A = a.y - b.y;
	B = b.x - a.x;
	if(B < 0) A = -A, B = -B;
	return {A, B};
}

vector<PLL> line;

void add(PLL nw){
	while(SZ(line)>1){
		int a = SZ(line);
		if(line[a-1].x == nw.x) return;
		PLL tmp1 = intersect(line[a-2], line[a-1]);
		PLL tmp2 = intersect(line[a-1], nw);
		if((__int128)tmp2.x*(__int128)tmp1.y <= (__int128)tmp1.x*(__int128)tmp2.y) line.pop_back();
		else break;
	}
	line.pb(nw);
}

LD calc(LD a, int b){
	return a*line[b].x + line[b].y;
}

LL L;
int n;

int main(){
	int i,j;
	LL a,b, dist0 = 2e18+2, distL = 2e18+2;
 	LD ans;
	scanf("%d %lld",&n,&L);
	for(i=1;i<=n;i++){
		scanf("%lld%lld",&a,&b);
		dist0 = min(dist0, a*a + b*b);
		distL = min(distL, (L-a)*(L-a) + b*b);
		tower[i] = {-a*2ll, a*a + b*b};
	}
	ans = (LD)max(dist0, distL);
    for(i=1;i<=n;i++) add(tower[i]);
    for(i = 0; i < SZ(line)-1; i++){
    	PLL tmp = intersect(line[i], line[i+1]);
    	LD tmp2 = (LD)tmp.x/tmp.y;
    	if(tmp2 < 0 || tmp2 > L) continue;
    	ans = max(ans, calc(tmp2, i) + tmp2*tmp2);
    }
    printf("%Lf",sqrt(ans));
    return 0;
}
/*
2 10
0 0
11 1

3 10
1 0
5 0
10 0

2 10
-5 3
12 2
*/

Compilation message (stderr)

mobile.cpp: In function 'int main()':
mobile.cpp:52:8: warning: unused variable 'j' [-Wunused-variable]
  int i,j;
        ^
mobile.cpp:55:7: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
  scanf("%d %lld",&n,&L);
  ~~~~~^~~~~~~~~~~~~~~~~
mobile.cpp:57:8: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   scanf("%lld%lld",&a,&b);
   ~~~~~^~~~~~~~~~~~~~~~~~

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