Submission #320567

#	Time	Username	Problem	Language	Result	Execution time	Memory
320567		arnold518	Sparklers (JOI17_sparklers)	C++14	100 / 100	36 ms	2924 KiB

sparklers

#include <bits/stdc++.h>
using namespace std;

typedef long long ll;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;

const int MAXN = 100000;
const ll INF = 1e18;

int N, K;
ll T, A[MAXN+10], B[MAXN+10];

bool decide(ll X)
{
	X*=2;
	if(T*X>(ll)1e9) return true;
	for(int i=1; i<=N; i++) B[i]=A[i]-i*T*X;

	int gl=1, gr=N;
	for(int i=1; i<=K; i++) if(B[gl]<=B[i]) gl=i;
	for(int i=K; i<=N; i++) if(B[gr]>=B[i]) gr=i;

	int l=K, r=K;
	ll lv=B[l], rv=B[r];
	while(gl<=l || r<=gr)
	{
		int bl=l, br=r;
		for(; l>=gl && B[l]>=rv; l--) lv=max(lv, B[l]);
		for(; r<=gr && B[r]<=lv; r++) rv=min(rv, B[r]);
		if(l==bl && r==br) return false;
	}

	l=1, r=N;
	lv=B[l], rv=B[r];
	while(l<=gl || gr<=r)
	{
		int bl=l, br=r;
		for(; l<=gl && B[l]>=rv; l++) lv=max(lv, B[l]);
		for(; r>=gr && B[r]<=lv; r--) rv=min(rv, B[r]);
		if(l==bl && r==br) return false;
	}
	return true;
}

int main()
{
	scanf("%d%d%lld", &N, &K, &T);
	for(int i=1; i<=N; i++) scanf("%lld", &A[i]);

	ll lo=-1, hi=1e9+10;
	while(lo+1<hi)
	{
		ll mid=lo+hi>>1;
		if(decide(mid)) hi=mid;
		else lo=mid;
	}
	printf("%lld\n", hi);
}

Compilation message (stderr)

sparklers.cpp: In function 'int main()':
sparklers.cpp:54:12: warning: suggest parentheses around '+' inside '>>' [-Wparentheses]
   54 |   ll mid=lo+hi>>1;
      |          ~~^~~
sparklers.cpp:48:7: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   48 |  scanf("%d%d%lld", &N, &K, &T);
      |  ~~~~~^~~~~~~~~~~~~~~~~~~~~~~~
sparklers.cpp:49:31: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   49 |  for(int i=1; i<=N; i++) scanf("%lld", &A[i]);
      |                          ~~~~~^~~~~~~~~~~~~~~

• Subtask 1: 30 / 30
• Subtask 2: 20 / 20
• Subtask 3: 50 / 50