제출 #629579

#	제출 시각	아이디	문제	언어	결과	실행 시간	메모리
629579		jh05013	메기 농장 (IOI22_fish)	C++17	52 / 100	800 ms	2097152 KiB

fish

#include <bits/stdc++.h>
using namespace std;
void OJize(){cin.tie(NULL);ios_base::sync_with_stdio(false);}

typedef long long ll;
const int IINF = 0x3f3f3f3f;
const ll LINF = 0x3f3f3f3f3f3f3f3f;
#define sz(X) (int)((X).size())
#define entire(X) X.begin(),X.end()
template <class T1, class T2>ostream&operator<<(ostream &os,pair<T1,T2>const&x){os<<'('<<x.first<<", "<<x.second<<')';return os;}
template <class Ch, class Tr, class Container>basic_ostream<Ch,Tr>&operator<<(basic_ostream<Ch,Tr>&os,Container const&x){os<<"[ ";for(auto&y:x)os<<y<<" ";return os<<"]";}

// NOTE: this is not a "sparse table" related to
// binary lifting, it's literally an array which is sparse!!
template<typename T>
struct SparseArray{
	// not actually sparse yet!!
	int n;
	vector<T> arr, sum, prefm, sufm;
	vector<bool> written;
	vector<int> nonempty;
	SparseArray(int N): n{N}, arr(N), sum(N),
		prefm(N), sufm(N),
		written(N){}

	void write(int i, T x){arr[i] = x; written[i] = true;}
	void init(){
		sum[0] = prefm[0] = arr[0];
		for(int i=1; i<n; i++){
			sum[i] = sum[i-1]+arr[i];
			prefm[i] = max(prefm[i-1], arr[i]);
		}
		for(int i=0; i<n; i++) if(written[i])
			nonempty.push_back(i);
		sufm[n-1] = arr[n-1];
		for(int i=n-2; i>=0; i--)
			sufm[i] = max(sufm[i+1], arr[i]);
	}

	T operator[](int i){return arr[i];}
	T prefsum(int i){return i>=0? sum[i] : (T)0;}
	T getsum(int l, int r){return prefsum(r) - prefsum(l);}
	T allmax(){return *max_element(entire(arr));}
	T prefmax(int i){return i>=0? prefm[i] : (T)0;}
	T sufmax(int i){return i<n? sufm[i] : (T)0;}
};

ll max_weights(int L, int n,
vector<int> X, vector<int> Y, vector<int> W){
	vector<SparseArray<ll>> grid(L, SparseArray<ll>(L+1));
	for(int i=0; i<L; i++)
		grid[i].write(0, 0), grid[i].write(L, 0);
	for(int i=0; i<n; i++) grid[X[i]].write(Y[i], (ll)W[i]);
	for(auto &A: grid) A.init();

	SparseArray<ll> dinc(L+1), ddec(L+1);
	dinc.init(); ddec.init();
	// column _,
	// last column height j,
	// next will increase/decrease
	for(int i=1; i<L; i++){
		SparseArray<ll> ndinc(L+1), nddec(L+1);
		SparseArray<ll> incmaxer(L+1), decmaxer(L+1);
		for(int y0: grid[i-1].nonempty){
			incmaxer.write(y0, dinc[y0] - grid[i-1].prefsum(y0-1));
			decmaxer.write(y0, ddec[y0] + grid[i].prefsum(y0-1));
		}
		incmaxer.init(), decmaxer.init();
		for(int y: grid[i].nonempty){
			ll incy = 0, decy = 0;
			if(y == 0) incy = decy = ddec[0];
			if(y == L) incy = decy = max(ddec[0], dinc[L]);
			
			ll incmax = grid[i-1].prefsum(y-1) + incmaxer.prefmax(y-1);
			incy = max(incy, incmax);
			if(y == L) decy = max(decy, incmax);
			ll decmax = -grid[i].prefsum(y-1) + decmaxer.sufmax(y+1);
			decy = max(decy, decmax);
			ndinc.write(y, incy);
			nddec.write(y, decy);
		}
		ndinc.init(); ddec.init();
		dinc = ndinc, ddec = nddec;
	}

	return max(dinc.allmax(), ddec.allmax());
}

#ifdef jh
int main(){OJize();
	int n; cin>>n;
	vector<int> X, Y, W;
	for(int i=0; i<n; i++) for(int j=0; j<n; j++){
		int x; cin>>x;
		if(x){
			X.push_back(j);
			Y.push_back(n-1-i);
			W.push_back(x);
		}
	}
	cout << max_weights(n, sz(X), X, Y, W);
}
#endif

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