Submission #24950

#	Time	Username	Problem	Language	Result	Execution time	Memory
24950		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],dp[N][N];
vector<int> d,l;
bool vis[N][N];
int n;

ll c;

bool check(ll mid) {
	for(int j=0;j<n;++j)
		dp[j][j] = INF;
	memset(vis,0,sizeof vis);
	for (int len = 2; len <= n; ++len) {
		for (int i = 0; i + len <= n; ++i) {
			int j = i + len - 1;
			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 (dp[i][j] > dp[i + 1][j])
				dp[i][j] = dp[i + 1][j];
			if (dp[i][j] > dp[i][j - 1])
				dp[i][j] = dp[i][j - 1];
		}
	}
	bool ok = false;
	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<L[i] + c + d[j])
				fage3 = L[i] + c + d[j];
			if (fage3 > mid)
				break;
			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] = true;
				ok = true;
			}

			if (j != n - 1)
				fage3 += l[j];
		}
	}
	if (!ok)
		return false;
	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 < R[i] + c + d[j])
				fage3 = R[i] + c + d[j];
 
			if (fage3 > mid)
				break;
			if (mxL[j] <= mid && vis[j][i]) {
				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));
	}
	ll lo = 0 , hi = 1e9*(N+3),best = -1;
	while(lo <= hi){
		ll mid = (lo + hi)/2;
		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