Submission #60244

#	Time	Username	Problem	Language	Result	Execution time	Memory
60244		ainta	Sparklers (JOI17_sparklers)	C++17	100 / 100	70 ms	12384 KiB

sparklers

#include<cstdio>
#include<algorithm>
#define N_ 101000
using namespace std;
int n, st, n1, n2, D[N_];
long long T, INF = 1e9, X[N_];
long long A[N_], B[N_], AA[N_], BB[N_];
struct point {
	int pv;
	long long Mn, Mx;
}w[N_];
bool Do() {
	int i, cnt = 0;
	n1--, n2--;
	long long Mx = -4e18, Mn = 4e18;
	for (i = 0; i <= n2; i++) {
		Mn = min(Mn, B[i]);
		if (Mx <= B[i]) {
			Mx = B[i];
			w[cnt++] = { i,Mn,Mx };
			Mn = B[i];
		}
	}
	for (i = 0; i < cnt; i++) {
		if (w[i].Mn + A[0] < 0)break;
	}
	D[0] = i - 1;
	if (D[0] == -1)return false;
	for (i = 1; i <= n1; i++) {
		if (w[D[i - 1]].Mx + A[i] < 0)return false;
		int pv = D[i - 1];
		while (pv < cnt - 1 && w[pv + 1].Mn + A[i] >= 0)pv++;
		D[i] = pv;
	}
	return w[D[n1]].pv == n2;
}
bool Pos(long long KK) {
	long long L = T*KK;
	if (L >= 1e9)return true;
	int i, j;
	for (i = st; i >= 1; i--) {
		AA[i] = X[i] + L * 2 * (st - i);
	}
	for (i = st; i <= n; i++) {
		BB[i] = -(X[i] - L * 2 * (i - st));
	}
	int pv1 = st, pv2 = st;
 
	for (i = st; i >= 1; i--) if (AA[pv1] < AA[i])pv1 = i;
	for (i = st; i <= n; i++) if (BB[pv2] < BB[i])pv2 = i;
	n1 = 0, n2 = 0;
	for (i = st; i >= pv1; i--)  A[n1++] = AA[i];
	for (i = st; i <= pv2; i++)  B[n2++] = BB[i];
	if (!Do())return false;
 
	n1 = 0, n2 = 0;
	for (i = 1; i <= pv1; i++)  A[n1++] = AA[i];
	for (i = n; i >= pv2; i--)  B[n2++] = BB[i];
	if (!Do())return false;
	return true;
 
}
int main() {
	int i;
	scanf("%d%d%lld", &n, &st, &T);
	for (i = 1; i <= n; i++) {
		scanf("%lld", &X[i]);
	}
	long long b = 0, e = 1e9, mid, res;
	while (b <= e) {
		mid = (b + e) / 2;
		if (Pos(mid)) {
			res = mid;
			e = mid - 1;
		}
		else b = mid + 1;
	}
	printf("%d\n", res);
}

Compilation message (stderr)

sparklers.cpp: In function 'bool Pos(long long int)':
sparklers.cpp:40:9: warning: unused variable 'j' [-Wunused-variable]
  int i, j;
         ^
sparklers.cpp: In function 'int main()':
sparklers.cpp:78:20: warning: format '%d' expects argument of type 'int', but argument 2 has type 'long long int' [-Wformat=]
  printf("%d\n", res);
                    ^
sparklers.cpp:65:7: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
  scanf("%d%d%lld", &n, &st, &T);
  ~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~
sparklers.cpp:67:8: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   scanf("%lld", &X[i]);
   ~~~~~^~~~~~~~~~~~~~~

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