Submission #24945

#	Time	Username	Problem	Language	Result	Execution time	Memory
24945		Hiasat	Shortcut (IOI16_shortcut)	C++14	38 / 100	2000 ms	81376 KiB

shortcut

#include "shortcut.h"
#include <bits/stdc++.h>

using namespace std;

typedef long long ll;

const int N = 3000;
const ll INF = 1e18;
ll L[N],R[N],mxL[N],mxR[N],pre[N];
vector<int> d,l;
bool vis[N][N];
ll dp[N][N];
int n;

ll c;

bool check(ll mid){
	for(int len = 1; len <= n ; ++len){
		for(int i = n-len ; i>=0 ; --i){
			int j = i + len - 1;
			if(len==1){
				dp[i][j]= INF;
				continue;
			}
			if(pre[j]-pre[i] +d[i]+d[j] > mid)
				dp[i][j]=(pre[j]-pre[i]) - d[i] - d[j];
			else
				dp[i][j]=INF;
/*			if(i == 1 && j == 2){
				cout << (pre[j]-pre[i]) + d[i] + d[j] << endl;
			}*/
			dp[i][j] = min(dp[i][j],min(dp[i+1][j],dp[i][j-1]));
		}
	}
//	cout << dp[0][3] << endl;
	memset(vis,0,sizeof vis);
	for(int i = 0 ; i < n ; ++i){
		if(mxL[i] > mid)
			continue;
		ll fage3 = -INF;
		ll csum = 0;
		for (int j = i+1; j < n; ++j){
			csum += l[j-1];
			if(L[j]+d[j] > mid)
				fage3 = max(fage3,L[i]+c+d[j]);
			if(fage3 > mid)
				break;
/*			if(i == 1 && j == 3){
				cout << fage3 << " " << L[i] << " " << d[j] << " " << csum+c-dp[i][j] << endl;
			}*/
		/*	if(i == 1 && j == 2){
				cout << dp[i][j] << " " <<  csum << endl;
			}*/
			if(min(csum,c)+L[i]+R[j]<=mid && mxR[j]<=mid && (dp[i][j] ==INF || csum+c-dp[i][j]<=mid)){
				vis[i][j] = 1;
			}
			if(j != n-1)
				fage3 += l[j];
		}
	}
	for(int i = n-1 ; i >= 0 ;--i){
		if(mxR[i] > mid)
			continue;
		ll fage3 = -INF;
		for (int j = i-1; j>= 0 ;j--){
			if(R[j]+d[j] > mid)
				fage3 = max(fage3,R[i]+c+d[j]);
			
			if(fage3 > mid)
				break;
			if(mxL[j]<=mid && vis[j][i]){
				//cout << "HERE " << j << " " << i << endl;
				return true;
			}
			if(j != 0)
				fage3 += l[j-1];
		}
	}
	return false;
}
ll find_shortcut(int n, vector<int> l, vector<int> d, int c){
	if(n>3000)
		return -1;
	::n=n;
	::d=d;
	::c=c;
	::l=l;
	for (int i = 0; i < n; ++i){
		L[i] = d[i];
		if(i)
			pre[i] = l[i-1] + pre[i-1];
		if(i)
			L[i] = max(L[i-1]+l[i-1],L[i]);
		mxL[i] = max(i?mxL[i-1]:0,d[i]+ (i?L[i-1]+l[i-1]:0));
	}
	for(int i = n - 1 ; i >= 0 ; i--){
		R[i] = d[i];
		if(i != n-1)
			R[i] = max(R[i],R[i+1]+l[i]);
		mxR[i] = max(i!=n-1?mxR[i+1]:0,d[i] + (i!=n-1?R[i+1]+l[i]:0));
	}
	//cout << "HASAN " << check(100) << endl;
	//return 0;
	ll lo = *max_element(d.begin(),d.end()) , hi = 1e9*(N+3),best = -1;
	while(lo <= hi){
		ll mid = (lo + hi)/2;
	//	cout << mid << " " << check(mid) << endl;
		if(check(mid)){
			best = mid;
			hi = mid -1;
		}else{
			lo = mid + 1;
		}
	}
	assert(best!=-1);
    return best;
}

• Subtask 1: 9 / 9
• Subtask 2: 14 / 14
• Subtask 3: 8 / 8
• Subtask 4: 7 / 7
• Subtask 5: 0 / 33
• Subtask 6: 0 / 22
• Subtask 7: 0 / 4
• Subtask 8: 0 / 3