AcWing 301 任务安排2

这道题考察凸包

代码

#include <iostream>
#include <algorithm>
#include <cstring>

using namespace std;

const int N = 3e5 + 10;

int n, s;

long long t[N], c[N], q[N];

long long f[N];

int main()
{
	scanf("%d%d", &n, &s);
	
	for (int i = 1; i <= n; i ++ )
	{
		scanf("%lld%lld", &t[i], &c[i]);
		t[i] += t[i - 1];
		c[i] += c[i - 1];
	}
	
	int hh = 0, tt = 0;
	q[0] = 0;
	
	for (int i = 1; i <= n; i ++ )
	{
//		斜率比较，判断队头有没有保留的必要
		while (hh < tt && (f[q[hh + 1]] - f[q[hh]]) <= (t[i] + s) * (c[q[hh + 1]] - c[q[hh]])) hh ++;
		int j = q[hh];
		f[i] = f[j] - (t[i] + s) * c[j] + t[i] * c[i] + s * c[n];
		while (hh < tt && (__int128)(f[q[tt]] - f[q[tt - 1]]) * (c[i] - c[q[tt - 1]]) >= (__int128)(f[i] - f[q[tt - 1]]) * (c[q[tt]] - c[q[tt - 1]])) tt --;
		q[ ++ tt] = i;
	}
	
	printf("%lld\n", f[n]);
	
	return 0;
}