[POJ 1180] Batch Scheduling

#include<iostream>
#include<stdio.h>
#include<algorithm>
#include<string.h>
#include<queue> 
using namespace std;
#define MAXN 100010
typedef long long ll;
typedef long double ld;
typedef unsigned long long ull;

int n , S , l , r;
int t[MAXN] , c[MAXN] , sumt[MAXN] , sumc[MAXN] , f[MAXN] , q[MAXN];

template <typename T> inline void chkmax(T &x,T y) { x = max(x,y); }
template <typename T> inline void chkmin(T &x,T y) { x = min(x,y); }
template <typename T> inline void read(T &x)
{
    T f = 1; x = 0;
    char c = getchar();
    for (; !isdigit(c); c = getchar()) if (c == ‘-‘) f = -f;
    for (; isdigit(c); c = getchar()) x = (x << 3) + (x << 1) + c - ‘0‘;
    x *= f;
}
int main()
{
        
        read(n); read(S);
        for (int i = 1; i <= n; i++)
        {
                read(t[i]);
                read(c[i]);
                sumt[i] = sumt[i - 1] + t[i];
                sumc[i] = sumc[i - 1] + c[i];
        }
        f[q[l = r = 1]] = 0;
        for (int i = 1; i <= n; i++)
        {
                while (l < r && f[q[l + 1]] - f[q[l]] <= (S + sumt[i]) * (sumc[q[l + 1]] - sumc[q[l]])) ++l;
                f[i] = f[q[l]] - (S + sumt[i]) * sumc[q[l]] + sumt[i] * sumc[i] + S * sumc[n];
                while (l < r && (f[i] - f[q[r]]) * (sumc[q[r]] - sumc[q[r - 1]]) <= (f[q[r]] - f[q[r - 1]]) * (sumc[i] - sumc[q[r]])) --r;
                q[++r] = i;         
        }
        printf("%d\n" , f[n]);
        
        return 0;
    
}