Bzoj 1597 Usaco Mar land purchase slope optimization DP

The main topic: give some planks, now to buy these planks. The purchase rule is that some planks can be bought together, and then the price is the maximum length multiplied by the maximum width. The minimum cost of purchasing all wood planks.

Idea: If a plank's length is smaller than a plank, and the width is smaller than a plank, then this plank can be ruled out. Sort all the planks according to the length of x, then remove the excluded planks, and the remaining planks are the ones with the X-values falling and the Y-values rising. In this case we buy a continuous section of the cost is X[J] * y[i], and then the DP equation is very simple: f[i] = f[j]-x[j + 1] * y[i].

Notice the data range, write a slope optimization on the water over.

CODE:

#include <cstdio> #include <cstring> #include <iostream> #include <algorithm> #define MAX 50010using namespace Std;    struct complex{int x, y;         BOOL blocked;    BOOL operator < (const Complex &a) const {return x > a.x;    } void Read () {scanf ("%d%d", &x,&y); }}src[max],point[max];         struct point{long long x, y; Point (Long long _ = 0,long Long __ = 0): X (_), Y (__) {}}q[max]; int Cnt,total;long long F[max];int front,tail;    Inline double getslope (const point &a,const point &b) {if (a.x = = b.x) return 1e15; Return (double) (A.Y-B.Y)/(a.x-b.x);}    inline void Insert (long long X,long long y) {point now (x, y);        while (Tail-front >= 2) if (Getslope (Q[tail],now) < Getslope (Q[tail-1],q[tail]))--tail;    else break; Q[++tail] = Now;} Inline point Getans (double slope) {while (Tail-front >= 2) if (Getslope (Q[front + 1],q[front + 2]) < slope ) ++fRont;    else break; return Q[front + 1];}    int main () {CIN >> cnt; for (int i = 1; I <= cnt; ++i) Src[i].    Read ();    Sort (src + 1,src + cnt + 1);    int now = 0;        for (int i = 1; I <= cnt, ++i) {if (src[i].y <= now) src[i].blocked = true;    else now = SRC[I].Y;    } for (int i = 1; I <= cnt; ++i) if (!src[i].blocked) point[++total] = Src[i];        for (int i = 1, i <= total; ++i) {Insert (-point[i].x,f[i-1]);        Point ans = Getans (POINT[I].Y);    F[i] = ans.y-point[i].y * ans.x;    } cout << f[total] << Endl; return 0;}

Bzoj 1597 Usaco Mar land purchase slope optimization DP