Submission #1079693

#	Time	Username	Problem	Language	Result	Execution time	Memory
1079693		allin27x	Radio Towers (IOI22_towers)	C++17	14 / 100	689 ms	11712 KiB

towers

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

const int MAXN = 1e5+4;
vector<int> h;
vector<int> lc,rc,a;
int pr[MAXN];
int inited = 0;

int fl[MAXN];
int fr[MAXN];

int sum (int l, int r) {
	if (l > r) return 0;
	if (l==0) return pr[r];
	return pr[r] - pr[l-1];
}

int dfs(int i, int d){
	if (i==-1) return 0;
	if (lc[i]==-1 && rc[i]==-1) return -a[i];
	int lans = dfs(lc[i],d);
	int rans = dfs(rc[i],d);
	if (lans < 0 && a[i] - d >= -lans) lans = 1;
	if (rans < 0 && a[i] - d >= -rans) rans = 1;
	if (lans < 0) {
		lc[lc[i]] = -2; rc[lc[i]] = -2;
		lc[i] = -1;
	}
	if (rans < 0) {
		lc[rc[i]] = -2; rc[rc[i]] = -2;
		rc[i] = -1;
	}
	if (!lans) return rans; if (!rans) return lans;
	if (lans < 0 && rans < 0) return max(lans,rans);
	if (lans < 0) return rans;
	if (rans < 0) return lans;
	return lans + rans;
}

signed helper(signed l, signed r, int d){
	int sz = r-l+1;
	a.assign(sz,0); for (int i=l; i<=r; i++) a[i-l] = h[i];

	a.push_back(3e9);
	stack<int> st; st.push(sz);
	lc.assign(sz+1,-1); rc.assign(sz+1,-1);

	for (int i=0; i<sz; i++){
		int last = -1;
		while (a[i] > a[st.top()]) {
			last=st.top();
			st.pop();
		}
		lc[i] = last;
		rc[st.top()]=i;
		st.push(i);
	}
	return dfs(sz,d);
}


void init(signed N, std::vector<signed> H){
	h.resize(N); for (int i = 0; i < N; i++) h[i] = H[i];
}

void init0(int d) {
	helper(0, h.size()-1, d);
	pr[0] = (lc[0]==-1 && rc[0]==-1);
	for (int i=1; i<h.size(); i++) pr[i] = pr[i-1] + (lc[i]==-1 && rc[i]==-1);
	int rs = 1e9;
	for (int i=h.size()-1; i>=0; i--) {
		if (lc[i]!=-2) rs = i;
		fl[i] = rs;
	}
	rs = -1;
	for (int i=0; i<h.size(); i++) {
		if (lc[i]!=-2) rs = i;
		fr[i] = rs;
	}
}


signed max_towers(signed l, signed r, signed d) {
	if (!inited) init0(d), inited = 1;
	l = fl[l]; r = fr[r];
	if (r-l <= 1) return 1;
	int s = sum(l+1,r-1);
	s += rc[l] == -1;
	s += lc[r] == -1;
	return s;
}

Compilation message (stderr)

towers.cpp: In function 'long long int dfs(long long int, long long int)':
towers.cpp:35:2: warning: this 'if' clause does not guard... [-Wmisleading-indentation]
   35 |  if (!lans) return rans; if (!rans) return lans;
      |  ^~
towers.cpp:35:26: note: ...this statement, but the latter is misleadingly indented as if it were guarded by the 'if'
   35 |  if (!lans) return rans; if (!rans) return lans;
      |                          ^~
towers.cpp: In function 'void init0(long long int)':
towers.cpp:71:17: warning: comparison of integer expressions of different signedness: 'long long int' and 'std::vector<long long int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   71 |  for (int i=1; i<h.size(); i++) pr[i] = pr[i-1] + (lc[i]==-1 && rc[i]==-1);
      |                ~^~~~~~~~~
towers.cpp:78:17: warning: comparison of integer expressions of different signedness: 'long long int' and 'std::vector<long long int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   78 |  for (int i=0; i<h.size(); i++) {
      |                ~^~~~~~~~~

• Subtask 1: 0 / 4
• Subtask 2: 0 / 11
• Subtask 3: 0 / 12
• Subtask 4: 14 / 14
• Subtask 5: 0 / 17
• Subtask 6: 0 / 19
• Subtask 7: 0 / 23