#pragma GCC optimize("Ofast")
/**
* Author: Sergey Kopeliovich ([email protected])
*/
#define VERSION "0.1.5"
#include <cassert>
#include <cstdio>
#include <algorithm>
/** Fast allocation */
#define FAST_ALLOCATOR_MEMORY (1024*1024*20)
#ifdef FAST_ALLOCATOR_MEMORY
int allocator_pos = 0;
char allocator_memory[(int)FAST_ALLOCATOR_MEMORY];
inline void * operator new ( size_t n ) {
char *res = allocator_memory + allocator_pos;
allocator_pos += n;
assert(allocator_pos <= (int)FAST_ALLOCATOR_MEMORY);
return (void *)res;
}
inline void operator delete ( void * ) noexcept { }
//inline void * operator new [] ( size_t ) { assert(0); }
//inline void operator delete [] ( void * ) { assert(0); }
#endif
/** Fast input-output */
template <class T = int> inline T readInt();
inline double readDouble();
inline int readUInt();
inline int readChar(); // first non-blank character
inline void readWord( char *s );
inline bool readLine( char *s ); // do not save '\n'
inline bool isEof();
inline int getChar();
inline int peekChar();
inline bool seekEof();
inline void skipBlanks();
template <class T> inline void writeInt( T x, char end = 0, int len = -1 );
inline void writeChar( int x );
inline void writeWord( const char *s );
inline void writeDouble( double x, int len = 0 );
inline void flush();
static struct buffer_flusher_t {
~buffer_flusher_t() {
flush();
}
} buffer_flusher;
/** Read */
static const int buf_size = 4096;
static unsigned char buf[buf_size];
static int buf_len = 0, buf_pos = 0;
inline bool isEof() {
if (buf_pos == buf_len) {
buf_pos = 0, buf_len = fread(buf, 1, buf_size, stdin);
if (buf_pos == buf_len)
return 1;
}
return 0;
}
inline int getChar() {
return isEof() ? -1 : buf[buf_pos++];
}
inline int peekChar() {
return isEof() ? -1 : buf[buf_pos];
}
inline bool seekEof() {
int c;
while ((c = peekChar()) != -1 && c <= 32)
buf_pos++;
return c == -1;
}
inline void skipBlanks() {
while (!isEof() && buf[buf_pos] <= 32U)
buf_pos++;
}
inline int readChar() {
int c = getChar();
while (c != -1 && c <= 32)
c = getChar();
return c;
}
inline int readUInt() {
int c = readChar(), x = 0;
while ('0' <= c && c <= '9')
x = x * 10 + c - '0', c = getChar();
return x;
}
template <class T>
inline T readInt() {
int s = 1, c = readChar();
T x = 0;
if (c == '-')
s = -1, c = getChar();
else if (c == '+')
c = getChar();
while ('0' <= c && c <= '9')
x = x * 10 + c - '0', c = getChar();
return s == 1 ? x : -x;
}
inline double readDouble() {
int s = 1, c = readChar();
double x = 0;
if (c == '-')
s = -1, c = getChar();
while ('0' <= c && c <= '9')
x = x * 10 + c - '0', c = getChar();
if (c == '.') {
c = getChar();
double coef = 1;
while ('0' <= c && c <= '9')
x += (c - '0') * (coef *= 1e-1), c = getChar();
}
return s == 1 ? x : -x;
}
inline void readWord( char *s ) {
int c = readChar();
while (c > 32)
*s++ = c, c = getChar();
*s = 0;
}
inline bool readLine( char *s ) {
int c = getChar();
while (c != '\n' && c != -1)
*s++ = c, c = getChar();
*s = 0;
return c != -1;
}
/** Write */
static int write_buf_pos = 0;
static char write_buf[buf_size];
inline void writeChar( int x ) {
if (write_buf_pos == buf_size)
fwrite(write_buf, 1, buf_size, stdout), write_buf_pos = 0;
write_buf[write_buf_pos++] = x;
}
inline void flush() {
if (write_buf_pos) {
fwrite(write_buf, 1, write_buf_pos, stdout), write_buf_pos = 0;
fflush(stdout);
}
}
template <class T>
inline void writeInt( T x, char end, int output_len ) {
if (x < 0)
writeChar('-'), x = -x;
char s[24];
int n = 0;
while (x || !n)
s[n++] = '0' + x % 10, x /= 10;
while (n < output_len)
s[n++] = '0';
while (n--)
writeChar(s[n]);
if (end)
writeChar(end);
}
inline void writeWord( const char *s ) {
while (*s)
writeChar(*s++);
}
inline void writeDouble( double x, int output_len ) {
if (x < 0)
writeChar('-'), x = -x;
int t = (int)x;
writeInt(t), x -= t;
writeChar('.');
for (int i = output_len - 1; i > 0; i--) {
x *= 10;
t = std::min(9, (int)x);
writeChar('0' + t), x -= t;
}
x *= 10;
t = std::min(9, (int)(x + 0.5));
writeChar('0' + t);
}
///////////////////////////////////////////////////////////////////////////////////////////////
#include <bits/stdc++.h>
using namespace std;
#define mp make_pair
#define pb push_back
#define FAST_IO ios_base::sync_with_stdio(false); cin.tie(0); cout.tie(0)
#define FILE_IO(x) freopen((string(x) + ".in").c_str(), "r", stdin); freopen((string(x) + ".out").c_str(), "w", stdout)
#define f first
#define s second
#define x1 x1qwer
#define y1 y1qwer
#define right right123
#define left left123
#define foreach(it, v) for (auto it : v)
#define rep(it, n) for (int it = 0; it < n; ++it)
#define forin(it, l, r) for (int it = l; it < r; ++it)
#define all(x) x.begin(), x.end()
typedef long long ll;
typedef unsigned long long ull;
typedef long double ld;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;
const double DINF = numeric_limits<double>::infinity();
const ll MOD = 1e9 + 7;
const double EPS = 1e-7;
ll gcd(ll a, ll b) { return b ? gcd(b, a % b) : a; }
mt19937 mmtw_(MOD);
uniform_int_distribution<ll> rd_;
ll randomll() { return rd_(mmtw_);}
ll rnd(ll x, ll y) { return rd_(mmtw_) % (y - x + 1) + x; }
////////////////////////////////////////////////////////////////////////////////////////////////
struct pt {
int x, y;
int id;
};
inline bool operator==(const pt &a, const pt &b) {
return a.x == b.x && a.y == b.y;
}
inline pt operator-(const pt &a) {
return {-a.x, -a.y};
}
inline pt operator-(const pt &a, const pt &b) {
return {a.x - b.x, a.y - b.y};
}
inline ll dot(const pt &a, const pt &b) {
return 1LL * a.x * b.x + 1LL * a.y * b.y;
}
inline ll cross(const pt &a, const pt &b) {
return 1LL * a.x * b.y - 1LL * a.y * b.x;
}
inline ll dd0(const pt &a) {
return dot(a, a);
}
const int MAXN = 2e5 + 5;
int n;
pt a[MAXN];
bool used[MAXN];
int ord[MAXN];
inline int md(int x) {
if (x >= n) return x - n;
if (x < 0) return x + n;
return x;
}
int findLowest() {
int s = 0;
for (int i = 0; i < n; ++i) {
ll cr = cross(a[i], a[s] - a[i]);
if (cr > 0 || (cr == 0 && dd0(a[i]) < dd0(a[s]))) {
s = i;
}
}
return s;
}
int findHighest() {
int t = 0;
for (int i = 0; i < n; ++i) {
ll cr = cross(a[i], a[t] - a[i]);
if (cr < 0 || (cr == 0 && dd0(a[i]) < dd0(a[t]))) {
t = i;
}
}
return t;
}
struct cmp {
bool operator()(int i, int j) {
if (i == j) return false;
if (cross(a[i], a[j]) <= 0) {
return cross(a[j + 1] - a[j], a[i] - a[j]) > 0;
} else {
return cross(a[i + 1] - a[i], a[j] - a[i]) < 0;
}
}
};
signed main() {
// FAST_IO;
// cin >> n;
n = readInt();
rep(i, n) {
// cin >> a[i].x >> a[i].y;
a[i].x = readInt();
a[i].y = readInt();
a[i].id = i + 1;
}
assert(n > 2);
int lowest = findLowest();
if (cross(a[md(lowest - 1)] - a[lowest], a[md(lowest + 1)] - a[lowest]) < 0) {
reverse(a, a + n);
}
rotate(a, a + findLowest(), a + n);
n = findHighest() + 1;
for (int i = 0; i < n; ++i) {
ord[i] = i;
}
sort(ord, ord + n, [](int i, int j){
ll cr = cross(a[i], a[j]);
if (cr != 0) return cr > 0;
return dd0(a[i]) < dd0(a[j]);
});
vector<int> res;
set<int, cmp> s;
for (int ii = 0; ii < n; ++ii) {
int i = ord[ii];
bool add = (i + 1 < n && cross(a[i], a[i + 1] - a[i]) > 0);
if (used[i]) {
s.erase(s.find(i - 1));
}
if (!s.empty()) {
int f = *s.begin();
if (cross(a[f + 1] - a[f], a[i] - a[f]) > 0) res.push_back(a[i].id);
} else {
res.push_back(a[i].id);
}
if (add) {
s.insert(i);
used[i + 1] = true;
}
}
sort(all(res));
// cout << res.size() << '\n';
writeInt(res.size(), '\n');
for (auto it : res) {
// cout << it << ' ';
writeInt(it, ' ');
}
// cout << '\n';
writeChar('\n');
}
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
2 ms |
380 KB |
Output is correct |
| 2 |
Correct |
2 ms |
376 KB |
Output is correct |
| 3 |
Correct |
2 ms |
508 KB |
Output is correct |
| 4 |
Correct |
2 ms |
632 KB |
Output is correct |
| 5 |
Correct |
4 ms |
632 KB |
Output is correct |
| 6 |
Correct |
6 ms |
632 KB |
Output is correct |
| 7 |
Correct |
7 ms |
932 KB |
Output is correct |
| 8 |
Correct |
4 ms |
632 KB |
Output is correct |
| 9 |
Correct |
4 ms |
760 KB |
Output is correct |
| 10 |
Correct |
5 ms |
632 KB |
Output is correct |
| 11 |
Correct |
5 ms |
760 KB |
Output is correct |
| 12 |
Correct |
6 ms |
1016 KB |
Output is correct |
| 13 |
Correct |
11 ms |
1272 KB |
Output is correct |
| 14 |
Correct |
8 ms |
1400 KB |
Output is correct |
| 15 |
Correct |
11 ms |
1912 KB |
Output is correct |
| 16 |
Correct |
21 ms |
3580 KB |
Output is correct |
| 17 |
Correct |
31 ms |
2936 KB |
Output is correct |
| 18 |
Correct |
38 ms |
6392 KB |
Output is correct |
| 19 |
Correct |
44 ms |
7160 KB |
Output is correct |
| 20 |
Correct |
89 ms |
6644 KB |
Output is correct |
