Submission #254665

#	Time	Username	Problem	Language	Result	Execution time	Memory
254665		MarcoMeijer	Triangles (CEOI18_tri)	C++14	0 / 100	1 ms	384 KiB

tri

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

// macros
typedef long long ll;
typedef long double ld;
typedef pair<int, int> ii;
typedef pair<ll, ll> lll;
typedef tuple<int, int, int> iii;
typedef vector<int> vi;
typedef vector<ii> vii;
typedef vector<iii> viii;
typedef vector<ll> vll;
typedef vector<lll> vlll;
#define REP(a,b,c) for(int a=int(b); a<int(c); a++)
#define RE(a,c) REP(a,0,c)
#define RE1(a,c) REP(a,1,c+1)
#define REI(a,b,c) REP(a,b,c+1)
#define REV(a,b,c) for(int a=int(c-1); a>=int(b); a--)
#define FOR(a,b) for(auto& a : b)
#define all(a) a.begin(), a.end()
#define INF 1e9
#define EPS 1e-9
#define pb push_back
#define popb pop_back
#define fi first
#define se second
#define sz size()
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());

// input
template<class T> void IN(T& x) {cin >> x;}
template<class H, class... T> void IN(H& h, T&... t) {IN(h); IN(t...); }

// output
template<class T1, class T2> void OUT(const pair<T1,T2>& x);
template<class T> void OUT(const T& x) {cout << x;}
template<class H, class... T> void OUT(const H& h, const T&... t) {OUT(h); OUT(t...); }
template<class T1, class T2> void OUT(const pair<T1,T2>& x) {OUT(x.fi," ",x.se);}
template<class... T> void OUTL(const T&... t) {OUT(t..., "\n"); }

//===================//
//  Added libraries  //
//===================//

//===================//
//end added libraries//
//===================//

void program();
int main() {
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);
    cout.tie(NULL);
    program();
}


//===================//
//   begin program   //
//===================//

const int MX = 50000;

int n, m;
int SHUF[MX];
bool cw(int x, int y, int z) {
    return is_clockwise(SHUF[x],SHUF[y],SHUF[z]);
}
bool ccw(int x, int y, int z) {
    return !is_clockwise(SHUF[x],SHUF[y],SHUF[z]);
}
vi getOnSide(vi& pos, int x, int y, bool side) {
    vi ret;
    FOR(i,pos) {
        if(x == i || y == i) continue;
        if(cw(x,y,i) == side) ret.pb(i);
    }
    return ret;
}
int MEX(int x, int y) {
    RE1(i,3)
        if(x != i && y != i) return i;
}
bool isBeg(int i) {
    int mostCW = MEX(i,0);
    RE1(j,n) {
        if(j == i) continue;
        if(j == mostCW) continue;
        if(cw(i,mostCW,j)) mostCW = j;
    }
    RE1(j,n) {
        if(j == i) continue;
        if(j == mostCW) continue;
        if(cw(i,mostCW,j)) return 0;
    }
    return 1;
}

int origin, or2;
int S[MX], C[MX];

void program() {
    n = get_n();
    RE1(i,n) SHUF[i] = i;
    shuffle(SHUF+1,SHUF+n+1,rng);
    if(n == 3) {
        give_answer(3);
        return;
    }

    origin = 1;
    RE(i,n) S[i] = i+1;
    RE(i,n) if(S[i] == origin) swap(S[i], S[0]);
    or2 = MEX(origin,0);
    sort(S+1,S+n,[](int i, int j) {
        if(i == or2) return (bool)1;
        if(j == or2) return (bool)0;
        bool ccwi = ccw(origin,or2,i);
        bool ccwj = ccw(origin,or2,j);
        if(ccwi == ccwj)
            return cw(origin, i, j);
        return ccwi;
    });
    if(isBeg(1)) {
        m=0;
        C[m++] = S[n-1], C[m++] = S[0];
        int i=1;
        while(i < n) {
            if(ccw(C[m-2],C[m-1],S[i])) C[m++] = S[i++];
            else m--;
        }
        give_answer(m-1);
    } else {
        m=0;
        C[m++] = S[n-1], C[m++] = S[0];
        int i=1;
        S[n++] = S[or2];
        while(i < n) {
            if(ccw(C[m-2],C[m-1],S[i])) C[m++] = S[i++];
            else m--;
        }
        give_answer(m-2);
    }
}

Compilation message (stderr)

tri.cpp: In function 'int MEX(int, int)':
tri.cpp:85:1: warning: control reaches end of non-void function [-Wreturn-type]
 }
 ^

• Subtask 1: 0 / 15
• Subtask 2: 0 / 20
• Subtask 3: 0 / 20
• Subtask 4: 0 / 20
• Subtask 5: 0 / 25