Submission #417351

#	Time	Username	Problem	Language	Result	Execution time	Memory
417351		CSQ31	Rainforest Jumps (APIO21_jumps)	C++14	0 / 100	197 ms	40976 KiB

jumps

#include "jumps.h"
#include<bits/stdc++.h>
using namespace std;
#define pb push_back
#define fi first
#define se second
#define sz(a) (int)(a.size())
typedef long long int ll;
typedef pair<int,int> pii;
typedef vector<vector<int>> vii;
const int MAXN = 2e5+5;
int l[20][MAXN],r[20][MAXN],high[20][MAXN];
vector<int>H;
void init(int n, vector<int>h){
	H = h;
	H.insert(H.begin(),0);
	h.pb(1e9);
	stack<pii>stk;
	for(int i=0;i<=n+1;i++){
		while(!stk.empty() && stk.top().fi < h[i])stk.pop();
		if(!stk.empty())l[0][i] = stk.top().se;
		else l[0][i] = i;
		stk.push({h[i],i});
	}
	while(!stk.empty())stk.pop();
	for(int i=n+1;i>=0;i--){
	    while(!stk.empty() && stk.top().fi < h[i])stk.pop();
		if(!stk.empty())r[0][i] = stk.top().se;
		else r[0][i] = i;
		stk.push({h[i],i});
	}
	for(int i=0;i<=n+1;i++){
		high[0][i] = (H[r[0][i]] > H[l[0][i]])?r[0][i]:l[0][i];
	}
	for(int j=1;j<20;j++){
		for(int i=0;i<=n+1;i++){
			l[j][i] = l[j-1][l[j-1][i]];
			r[j][i] = r[j-1][r[j-1][i]];
			high[j][i] = high[j-1][high[j-1][i]];
		}
	}
	
}
//
int minimum_jumps(int a,int b,int c,int d){
	a++;
	b++;
	c++;
	d++;
	if(c == b+1){
		if(r[0][b] > d)return -1;
		return 1;
	}
	int mid = b+1;
	for(int j=19;j>=0;j--){
		if(r[j][mid] < c){
			mid = r[j][mid];
		}
	}
	if(H[b] > H[mid])return r[0][b]<=d?1:-1;
	//anything higher this mid point can be possibly "unreachable"
	//otherwise we are safe to use high edges
	int cur = b; 
	for(int j=19;j>=0;j--){
		if(l[j][cur] >= a && H[l[j][cur]] < H[mid])cur = l[j][cur];
	} 
	//we want to start at cur
	int ans = 0;
	if(l[0][cur] >= a){
	   if(r[0][l[0][cur]] <= d)return 1;
   }else{
	   
		//if l[0][cur] reachable we take it,else we can never go left again
		for(int j=19;j>=0;j--){
			if(H[high[j][cur]] <= H[mid]){
				ans+=(1<<j);
				cur = high[j][cur];
			}
		}
		if(cur == mid){
			if(r[0][mid] <= d)return ans+1;
			else return -1;
		}else{
			//since we cant jump right without >= h[mid]
			//we check if jumping left is reachable
			if(l[0][cur] && r[0][l[0][cur]] <= d)return ans+2;
		}
	}
	//we cant jump to the left anymore : ( 
	 for(int j=19;j>=0;j--){
		 if(r[j][cur] < c){
			 cur = r[j][cur];
			 ans+=(1<<j);
		 }
	 }
	if(r[0][cur] <= d && r[0][cur] >= c)return ans+1;
	else return -1;
}

• Subtask 1: 0 / 4
• Subtask 2: 0 / 8
• Subtask 3: 0 / 13
• Subtask 4: 0 / 12
• Subtask 5: 0 / 23
• Subtask 6: 0 / 21
• Subtask 7: 0 / 19