POJ - 1180 Batch Scheduling（斜率优化DP）

#include<cstdio>

typedef long long LL;
const int N = 300010;
LL sc[N], st[N], f[N];
int q[N], hh, tt;

int main()
{
	int n, s; scanf("%d%d", &n, &s);
	for (int i = 1; i <= n; i ++ )
	{
		scanf("%lld%lld", &st[i], &sc[i]);
		st[i] += st[i - 1];
		sc[i] += sc[i - 1];
	}
	hh = 0, tt = 0;
	for (int i = 1; i <= n; i ++ )
	{
		while (hh < tt && (f[q[hh + 1]] - f[q[hh]]) <=
		        (st[i] + s) * (sc[q[hh + 1]] - sc[q[hh]])) hh ++ ;

		f[i] = f[q[hh]] - (st[i] + s) * sc[q[hh]] + sc[i] * st[i] + s * sc[n];

		while (hh < tt && (f[q[tt]] - f[q[tt - 1]]) * (sc[i] - sc[q[tt]]) >=
		        (f[i] - f[q[tt]]) * (sc[q[tt]] - sc[q[tt - 1]])) tt -- ;
		q[ ++ tt] = i;
	}
	printf("%lld\n", f[n]);
	return 0;
}