Submission #55622

#	Time	Username	Problem	Language	Result	Execution time	Memory
55622		ksun48	Cultivation (JOI17_cultivation)	C++14	100 / 100	1272 ms	180312 KiB

cultivation

#include <bits/stdc++.h>
using namespace std;
typedef long long LL;

int r, c, n;
vector<pair<int,int> > seeds;
const int INF = 2100100100;
int best = INF;
set<int> tried;

vector<int> xlist;
int len;

int up[400][400];
int down[400][400];
int total[400][400];

struct maxqueue {
	vector<int> elements;
	vector<int> indices;
	int s;
	int len;
	maxqueue() : s(0), len(0), elements(0), indices(0) {}
};

void insert(maxqueue* m, int f){
	while(m->elements.size() > 0 && m->elements.size() > m->s && m->elements[m->elements.size()-1] <= f){
		m->elements.pop_back();
		m->indices.pop_back();
	}
	m->elements.push_back(f);
	m->indices.push_back(m->len);
	m->len++;
}
int get(maxqueue* m){
	return m->elements[m->s];
}
void pop(maxqueue *m, int idx){
	if(m->indices[m->s] == idx){
		m->s++;
	}
}

int ups[700];
int downs[700];
int totals[700];
int pos1[700];
int pos2[700];
int pos[700];

int lastc = 0;

void tryxfast(int x){
	if(x < 0 || (x+1) <= (r-1)/n || (LL)x >= (LL)best - (LL)lastc){
		return;
	}
	for(int i = 0; i < len; i++){
		pos1[i] = xlist[i] - x;
		pos2[i] = xlist[i] + 1;
	}
	merge(pos1, pos1 + len, pos2, pos2 + len, pos);

	int sz = len * 2;

	int a = 0;
	int b = 0;
	for(int i = 0; i < sz; i++){
		while(a + 1 < len && xlist[a+1] - x <= pos[i]) a++;
		while(b + 1 < len && xlist[b+1] + 1 <= pos[i]) b++;
		// a >= b
		ups[i] = up[a][b];
		downs[i] = down[a][b];
		totals[i] = total[a][b];
	}

	// two pointers: 
	int j = 0;
	maxqueue* upset    = new maxqueue();
	maxqueue* downset  = new maxqueue();
	maxqueue* totalset = new maxqueue();
	LL bestneed = best + 1;
	for(int i = 0; i < sz; i++){
		while(j < sz && pos[j] <= pos[i] + r - 1){
			insert(upset, ups[j]);
			insert(downset, downs[j]);
			insert(totalset, totals[j]);
			j++;
		}
		if(j == sz) break;
		int total = get(totalset);
		if(total < c+1){
			LL need = max((LL)get(upset) + (LL)get(downset), (LL)total - 1);
			bestneed = min(bestneed, need);
		}
		pop(upset, i);
		pop(downset, i);
		pop(totalset, i);
	}
	lastc = bestneed;
	best = min((LL)best, bestneed + (LL)x);
}

int main(){
	double st = clock();
	cin.sync_with_stdio(0); cin.tie(0);
	cin >> r >> c >> n;
	for(int i = 0; i < n; i++){
		int s, e;
		cin >> s >> e;
		s--; e--;
		seeds.push_back({e,s});
	}
	sort(seeds.begin(), seeds.end());
	set<int> xset;
	for(int i = 0; i < n; i++){
		swap(seeds[i].first, seeds[i].second);
		xset.insert(seeds[i].first);
	}
	xlist.push_back(-1);
	for(int x : xset){
		xlist.push_back(x);
	}
	len = xlist.size();

	// now n^2 log n
	for(int i = 0; i < xlist.size(); i++){
		vector<int> ins[xlist.size() + 1];
		vector<int> del[xlist.size() + 1];

		for(int k = 0; k < seeds.size(); k++){
			int p = seeds[k].first;
			if(p <= xlist[i]){
				ins[0].push_back(seeds[k].second);
				int jdel = lower_bound(xlist.begin(), xlist.end(), p) - xlist.begin();
				del[jdel].push_back(seeds[k].second);
			}
		}

		multiset<int> grass;
		grass.insert(-1);
		grass.insert(c);
		multiset<int> diffs;
		diffs.insert(-(c+1));
		for(int j = 0; j <= i; j++){
			for(int a : del[j]){
				int a1 = *(--grass.find(a));
				int a2 = *(++grass.find(a));
				diffs.erase(diffs.find(a1-a));
				diffs.erase(diffs.find(a-a2));
				diffs.insert(a1-a2);
				grass.erase(grass.find(a));
			}
			for(int a : ins[j]){
				grass.insert(a);
				int a1 = *(--grass.find(a));
				int a2 = *(++grass.find(a));
				diffs.erase(diffs.find(a1-a2));
				diffs.insert(a1-a);
				diffs.insert(a-a2);
			}
			total[i][j] = -*diffs.begin();
			up[i][j] = *(++grass.begin()) - 0;
			down[i][j] = c-1 - *(--(--grass.end()));
		}
	}

	set<int> trying;
	for(int i = 0; i < n; i++){
		for(int j = 0; j < n; j++){
			trying.insert(-(seeds[i].first + r-1 - seeds[j].first));
			trying.insert(-(seeds[i].first -   1 - seeds[j].first));
		}
	}
	vector<int> tries;
	for(int r : trying){
		tries.push_back(-r);
	}
	for(int j = 50000; j < 60000 && j < tries.size(); j++){
		lastc = 0;
		tryxfast(tries[tries.size()-1-j]);
	}
	for(int j = 80000; j < 100000 && j < tries.size(); j++){
		lastc = 0;
		tryxfast(tries[tries.size()-1-j]);
	}
	lastc = 0;
	for(int r : tries){
		if(clock() > st + 1.95 * CLOCKS_PER_SEC) break;
		tryxfast(r);
	}
	cout << best << '\n';
}

Compilation message (stderr)

cultivation.cpp: In constructor 'maxqueue::maxqueue()':
cultivation.cpp:22:6: warning: 'maxqueue::len' will be initialized after [-Wreorder]
  int len;
      ^~~
cultivation.cpp:19:14: warning:   'std::vector<int> maxqueue::elements' [-Wreorder]
  vector<int> elements;
              ^~~~~~~~
cultivation.cpp:23:2: warning:   when initialized here [-Wreorder]
  maxqueue() : s(0), len(0), elements(0), indices(0) {}
  ^~~~~~~~
cultivation.cpp: In function 'void insert(maxqueue*, int)':
cultivation.cpp:27:53: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  while(m->elements.size() > 0 && m->elements.size() > m->s && m->elements[m->elements.size()-1] <= f){
                                  ~~~~~~~~~~~~~~~~~~~^~~~~~
cultivation.cpp: In function 'int main()':
cultivation.cpp:126:19: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(int i = 0; i < xlist.size(); i++){
                 ~~^~~~~~~~~~~~~~
cultivation.cpp:130:20: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
   for(int k = 0; k < seeds.size(); k++){
                  ~~^~~~~~~~~~~~~~
cultivation.cpp:178:36: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(int j = 50000; j < 60000 && j < tries.size(); j++){
                                  ~~^~~~~~~~~~~~~~
cultivation.cpp:182:37: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(int j = 80000; j < 100000 && j < tries.size(); j++){
                                   ~~^~~~~~~~~~~~~~

• Subtask 1: 5 / 5
• Subtask 2: 10 / 10
• Subtask 3: 15 / 15
• Subtask 4: 30 / 30
• Subtask 5: 20 / 20
• Subtask 6: 20 / 20