BZOJ3437 小P的牧场

还是DP题写起来容易的说。。。

直接看zky的一图流好了（话说zky用的是三分？。。。给跪）

 

 1 /**************************************************************
 2     Problem: 3437
 3     User: rausen
 4     Language: C++
 5     Result: Accepted
 6     Time:1616 ms
 7     Memory:32056 kb
 8 ****************************************************************/
 9  
10 #include <cstdio>
11  
12 #define L q[l]
13 using namespace std;
14 typedef long long ll;
15 const int N = 1000005;
16  
17 int n, l, r;
18 ll f[N], g[N], q[N];
19 ll sum1[N], sum2;
20  
21 inline int read() {
22     int x = 0;
23     char ch = getchar();
24     while (ch < '0' || '9' < ch)
25         ch = getchar();
26     while ('0' <= ch && ch <= '9') {
27         x = x * 10 + ch - '0';
28         ch = getchar();
29     }
30     return x;
31 }
32  
33 inline ll calc1(int x, int y) {
34     return (ll) g[x] - g[y];
35 }
36  
37 inline ll calc2(int x, int y) {
38     return (ll) sum1[x] - sum1[y];
39 }
40  
41 inline bool pop_head(int x, int i) {
42     return calc1(q[x + 1], q[x]) < i * calc2(q[x + 1], q[x]);
43 }
44  
45 inline bool pop_tail(int x, int i) {
46     return calc1(i, q[x]) * calc2(q[x], q[x - 1]) < calc1(q[x], q[x - 1]) * calc2(i, q[x]);
47 }
48  
49 int main() {
50     int i, b;
51     n = read();
52     for (i = 1; i <= n; ++i)
53         f[i] = read();
54     for (l = r = 0, i = 1; i <= n; ++i) {
55         b = read();
56         sum1[i] = sum1[i - 1] + b;
57         sum2 += (ll) i * b;
58  
59         while (l < r && pop_head(l, i)) ++l;
60         f[i] += g[L] + i * (sum1[i] - sum1[L]) - sum2;
61         g[i] = f[i] + sum2;
62         while (l < r && pop_tail(r, i)) --r;
63         q[++r] = i;
64     }
65     printf("%lld\n", f[n]);
66     return 0;
67 }
View Code

 

posted on 2014-11-30 17:04  Xs酱~  阅读(220)  评论(0)  编辑  收藏  举报