Submission #905533

#	Time	Username	Problem	Language	Result	Execution time	Memory
905533		joonwu04	The Big Prize (IOI17_prize)	C++17	0 / 100	2 ms	2052 KiB

prize

#include "prize.h"
#include <iostream>

using namespace std;

int sub1(int st, int ed) {
	int mid = (st + ed) / 2;
	vector<int> v = ask(mid);
	int l = v[0], r = v[1];
	if(l == 1) return sub1(st, mid-1);
	else if(r == 1) return sub1(mid+1, ed);
	else return mid;
}

int ls[200100], rs[200100], maxLR;
// u = sum of cheapest V's left and right

bool isDiamond(int i);
void makeLR(int i);
int findDiamond(int st, int ed);

int sub2(int n) { // idx: 0 ~ n-1
	for(int i=0; i<n; i++) {
		ls[i] = -1; rs[i] = -1;
	}
	
	// find st, ed
	int st = 0, ed = n-1, stIdx = -1, edIdx = -1;
	maxLR = -1;
	while(st + ed < 473) {
		makeLR(st); makeLR(ed);
		
		// check if it is dia
		if(isDiamond(st)) return st;
		if(isDiamond(ed)) return ed;
		
		// if no then record maxlr
		if(ls[st] + rs[st] >= maxLR) {
			maxLR = ls[st] + rs[st];
			stIdx = st;
		}
		if(ls[ed] + rs[ed] >= maxLR) {
			maxLR = ls[ed] + rs[ed];
			edIdx = ed;
		}
		
		st++; ed--;
	}
	st = stIdx;
	ed = edIdx;
	
	return findDiamond(st, ed);
}

bool isDiamond(int i) {
	return ls[i] + rs[i] == 0;
}

void makeLR(int i) {
	if(ls[i] != -1 && rs[i] != -1) return;
	
	vector<int> v = ask(i);
	ls[i] = v[0]; rs[i] = v[1];
}

// st, ed are cheapest
int findDiamond(int st, int ed) {
	if(st == ed) {
		if(ls[st] + rs[st] == 0) return st;
		else return -1; 
	}
	
	// if st~ed, no prize
	if(ls[ed] - ls[st] == 0) return -1;
	
	int mid = (st + ed) / 2;
	makeLR(mid);
	if(isDiamond(mid)) return mid;
	
	// make led, rst
	int led = mid;
	while(/*led>=st*/ls[led] + rs[led] < maxLR) {
		led--;
		makeLR(led);
		if(isDiamond(led)) return led;
	}
	
	int rst = mid;
	while(/*rst<=ed*/ls[rst] + rs[rst] < maxLR) {
		rst++;
		makeLR(rst);
		if(isDiamond(rst)) return rst;
	}
	
	int resL = findDiamond(st, led);	// check initial condition
	int resR = findDiamond(rst, ed);
	
	return resL > resR ? resL:resR;
}

int find_best(int n) {
	return sub2(n);
}

• Subtask 1: 0 / 20
• Subtask 2: 0 / 80