斜率优化dp

模板题：loj10185

#include<cstdio>
#include<iostream>
using namespace std;
const int maxn = 300010;
inline int qread(){
    register int ch = getchar(), x = 0;
    while(ch < 48 || ch > 57)    ch = getchar();
    while(ch > 47 && ch < 58)    x = (x << 3) + (x << 1) + ch - 48, ch = getchar();
    return x;
}
int T[maxn], C[maxn], sumT[maxn], sumC[maxn], f[maxn];
int n, S;
int qu[maxn];
int head = 1, tail = 1;
int main(void){
    n = qread();
    S = qread();
    for(int i = 1; i <= n; ++i)
        T[i] = qread(), C[i] = qread();
    for(int i = 1; i <= n; ++i)
        sumT[i] = sumT[i - 1] + T[i], sumC[i] = sumC[i - 1] + C[i];
    for(int i = 1; i <= n; ++i){
        while(head < tail && f[qu[head + 1]] - f[qu[head]] <= (S + sumT[i]) * (sumC[qu[head + 1]] - sumC[qu[head]]))    ++head;
        f[i] = f[qu[head]  + sumT[i] * (sumC[i] - sumC[qu[head]) + S * (sumC[n] - sumC[qu[head]);
        while(head < tail && (f[qu[tail]] - f[qu[tail - 1]]) * (sumC[i] - sumC[qu[tail]]) >= (f[i] - f[qu[tail]]) * (sumC[qu[tail]] - sumC[qu[tail - 1]]))    --tail;
        qu[++tail] = i;
    }
    printf("%d\n", f[n]);        
}