HDOJ 1300 Pearls 斜率优化dp

原题连接：http://acm.hdu.edu.cn/showproblem.php?pid=1300

题意：

题目太长了。。自己看吧

题解：

看懂题目，就会发现这是个傻逼dp题，斜率优化一下就好

代码：

#include<iostream>
#include<cstring>
#include<vector>
#include<cstdio>
#define MAX_N 500
using namespace std;

typedef long long ll;

ll N;
ll sum[MAX_N];

ll dp[MAX_N];
ll a[MAX_N];
ll p[MAX_N];

double Y(int t){
    return dp[t];
}

double X(int t){
    return sum[t];
}

double Slope(int u,int v) {
    return (Y(u) - Y(v)) / (X(u) - X(v));
}

int que[MAX_N];
int T;
int main() {
    cin.sync_with_stdio(false);
    cin>>T;
    while (T--) {
        cin>>N;
        memset(dp,,sizeof(dp));
        memset(que,,sizeof(que));
        memset(sum,,sizeof(sum));
        for (int i = ; i <= N; i++) {
            cin >> a[i] >> p[i];
            sum[i] = sum[i - ] + a[i];
        }
        int front = , rear = ;
        que[rear++] = ;

        for (int i = ; i <= N; i++) {
            while (rear - front >  && Slope(que[front], que[front + ]) <= p[i])front++;
            int j = que[front];
            dp[i] = dp[j] + (sum[i] - sum[j] + ) * p[i];
            while (rear - front >  && Slope(que[rear - ], que[rear - ]) >= Slope(que[rear - ], i))rear--;
            que[rear++] = i;
        }
        cout << dp[N] << endl;
    }
    return ;
}