Submission #292254

#	Time	Username	Problem	Language	Result	Execution time	Memory
292254		tmwilliamlin168	Roller Coaster Railroad (IOI16_railroad)	C++14	100 / 100	293 ms	21556 KiB

railroad

#include "railroad.h"
#include <bits/stdc++.h>
using namespace std;

const int mxN=4e5;
int a[mxN], p[mxN];
array<int, 2> e[mxN];

int find(int x) {
	return x^p[x]?p[x]=find(p[x]):x;
}

bool join(int x, int y) {
	if((x=find(x))==(y=find(y)))
		return 0;
	p[x]=y;
	return 1;
}

long long plan_roller_coaster(vector<int> s, vector<int> t) {
	int n=s.size();
	vector<int> x=s;
	x.insert(x.end(), t.begin(), t.end());
	sort(x.begin(), x.end());
	iota(p, p+x.size(), 0);
	for(int i=0; i<n; ++i) {
		s[i]=lower_bound(x.begin(), x.end(), s[i])-x.begin();
		t[i]=lower_bound(x.begin(), x.end(), t[i])-x.begin();
		++a[s[i]];
		--a[t[i]];
		join(s[i], t[i]);
	}
	long long ans=0;
	for(int i=0; i+1<x.size(); ++i) {
		a[i+1]+=a[i];
		ans+=(long long)(x[i+1]-x[i])*max(a[i]-1, 0);
		if(a[i]^1)
			join(i, i+1);
		e[i]={x[i+1]-x[i], i};
	}
	sort(e, e+x.size()-1);
	for(int i=0; i<x.size()-1; ++i)
		if(join(e[i][1], e[i][1]+1))
			ans+=e[i][0];
	return ans;
}

Compilation message (stderr)

railroad.cpp: In function 'long long int plan_roller_coaster(std::vector<int>, std::vector<int>)':
railroad.cpp:34:18: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   34 |  for(int i=0; i+1<x.size(); ++i) {
      |               ~~~^~~~~~~~~
railroad.cpp:42:16: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   42 |  for(int i=0; i<x.size()-1; ++i)
      |               ~^~~~~~~~~~~

• Subtask 1: 11 / 11
• Subtask 2: 23 / 23
• Subtask 3: 30 / 30
• Subtask 4: 36 / 36