Submission #1083239

#	Time	Username	Problem	Language	Result	Execution time	Memory
1083239		Math4Life2020	Ancient Books (IOI17_books)	C++17	Compilation error	0 ms	0 KiB

books

// Source: https://usaco.guide/general/io

#include <bits/stdc++.h>
using namespace std;
using ll = long long; using pii = pair<ll,ll>;

int triv(int N) {
	for (ll i=0;i<N;i++) {
		int a0[2] = ask((int)i);
		if ((a0[0]+a0[1])==0) {
			return i;
		}
	}
}

map<ll,pii> pts;
ll N;
ll gm;
ll ans = -1;
vector<bool> asked;

ll process(ll x) {
	if (!asked[x]) {
		int a0[2] = ask((int)x);
		pts[x]={a0[0],a0[1]};
		asked[x]=1;
	}
	ll S = pts[x].first+pts[x].second;
	if (S==0) {
		return x;
	}
	if (S<gm) {
		ll y = -1;
		if (x>0 && !asked[x-1]) {
			y=max(y,process(x-1));
		}
		if (x<(N-1) && !asked[x+1]) {
			y=max(y,process(x+1));
		}
		return y;
	}
	return -1;
}

void query(ll a, ll b) {
	if ((a+1)==b) {
		return;
	}
	if (pts[a].first==pts[b].first) {
		return;
	}
	ll c = (a+b)/2;
	ans=max(ans,process(c));
	if (ans!=-1) {
		return;
	}
	auto A1 = pts.find(a); A1++;
	query(a,(*A1).first);
	auto B1 = pts.find(b); B1--;
	query((*B1).first,b);
}

int find_best(int N0) {
	N=N0;
	gm=0;
	ans = -1;
	pts.clear();
	asked.clear();
	for (ll i=0;i<N;i++) {
		asked.push_back(0);
	}
	if (N<=5000) {
		return triv(N);
	}
	ll r = (N-1)/500;
	for (ll i=1;i<=500;i++) {
		int a0[2] = ask((int)(i*r));
		asked[i*r]=1;
		pts[i*r]={a0[0],a0[1]};
	}
	for (auto A: pts) {
		pii p0 = A.second;
		gm = max(gm,p0.first+p0.second);
	}
	for (auto A: pts) {
		ll v = process(A.first);
		if (v!=-1) {
			return v;
		}
	}
	if (process(0)!=-1) {
		return 0;
	}
	if (process(N-1)!=-1) {
		return (N-1);
	}
	auto A = pts.begin(); auto B=A; B++;
	do {
		pii pa = (*A).second; pii pb = (*B).second;
		if ((pa.first+pa.second+pb.first+pb.second)==(2*gm)) {
			query((*A).first,(*B).first);
			if (ans != -1) {
				return ans;
			}
		}
		A++; B++;
	} while (B != pts.end());
}

Compilation message (stderr)

books.cpp: In function 'int triv(int)':
books.cpp:9:15: error: 'ask' was not declared in this scope
    9 |   int a0[2] = ask((int)i);
      |               ^~~
books.cpp: In function 'll process(ll)':
books.cpp:24:15: error: 'ask' was not declared in this scope
   24 |   int a0[2] = ask((int)x);
      |               ^~~
books.cpp: In function 'int find_best(int)':
books.cpp:77:15: error: 'ask' was not declared in this scope
   77 |   int a0[2] = ask((int)(i*r));
      |               ^~~
books.cpp: In function 'int triv(int)':
books.cpp:14:1: warning: control reaches end of non-void function [-Wreturn-type]
   14 | }
      | ^
books.cpp: In function 'int find_best(int)':
books.cpp:108:1: warning: control reaches end of non-void function [-Wreturn-type]
  108 | }
      | ^