#题解#洛谷 P3029 Cow Lineup S #双指针#离散化#

P3029 [USACO11NOV] Cow Lineup S - 洛谷

分析

1. 离散化，双指针

代码实现

#include<bits/stdc++.h>
using namespace std;
const int N = 1e5+10;
struct cow
{
	int pos, x;
} a[N];
bool cmp(cow x, cow y)
{
	return x.pos < y.pos;
}
map<int, int >m;
int main()
{
	ios::sync_with_stdio(0);
	cin.tie(0);
	cout.tie(0);
	int n;
	cin >> n;
	for (int i = 1; i <= n; i++)
	{
		cin >> a[i].pos >> a[i].x;
		m[a[i].x] = 0;
	}
	int kind = m.size();
	sort(a + 1, a + 1 + n, cmp);
//	for(int i=1;i<=n;i++)
//		cout<<a[i].x<<" "<<a[i].pos<<'\n';
	int cnt = 0;
	int min_cost = 1e9;
	int j = 1;
	for (int i = 1; i <= n; i++)
	{
		while (cnt < kind && j <= n)
		{
			if (m[a[j].x] == 0)
				cnt++;
			m[a[j].x]++;
			j++;
		}
		if (kind == cnt)
			min_cost = min(min_cost, a[j - 1].pos - a[i].pos);
		m[a[i].x]--;
		if (m[a[i].x] == 0)
			cnt--;
	}
	cout << min_cost;
	return 0;
}