BZOJ2424 [HAOI2010]订货

裸的费用流。。。。

建图方法：把每个月抽象成一个点

S向每个点连边，费用为当月购进价，容量无限大；每个点向T连边，费用为0，容量为当月卖出量

每个点向后一个月的点连边，费用为仓库储存费用m，容量为仓库的容量s

 

 1 /**************************************************************
 2     Problem: 2424
 3     User: rausen
 4     Language: C++
 5     Result: Accepted
 6     Time:0 ms
 7     Memory:1028 kb
 8 ****************************************************************/
 9  
10 #include <cstdio>
11 #include <algorithm>
12   
13 using namespace std;
14 const int inf = (int) 1e9;
15 const int N = 2005;
16 const int M = 10005;
17 struct edges{
18     int next, to, cost, f;
19 } e[M];
20 int tot = 1, n, m, s;
21 int first[N], d[N], g[N], q[M];
22 bool v[N];
23 int S, T, ans;
24   
25 inline int read(){
26     int x = 0, sgn = 1;
27     char ch = getchar();
28     while (ch < '0' || ch > '9'){
29         if (ch == '-') sgn = -1;
30         ch = getchar();
31     }
32     while (ch >= '0' && ch <= '9'){
33         x = x * 10 + ch - '0';
34         ch = getchar();
35     }
36     return sgn * x;
37 }
38   
39 inline void add_edge(int x, int y, int d, int c){
40     e[++tot].next = first[x];
41     first[x] = tot;
42     e[tot].to = y;
43     e[tot].f = d;
44     e[tot].cost = c;
45 }
46    
47 void add_Edges(int x, int y,int d, int c){
48     add_edge(x, y, d, c);
49     add_edge(y, x, 0, -c);
50 }
51    
52 inline int calc(){
53     int flow = inf;
54     for (int x = g[T]; x; x = g[e[x ^ 1].to])
55         flow = min(flow, e[x].f);
56     for (int x = g[T]; x; x = g[e[x ^ 1].to])
57         e[x].f -= flow, e[x ^ 1].f += flow;
58     return flow;
59 }
60    
61 bool spfa(){
62     for (int i = 1; i <= T; ++i)
63         d[i] = inf;
64     d[S] = 0, v[S] = 1;
65     q[1] = S;
66     int x, y;
67     for(int l = 1, r = 1; l <= r; ++l){
68         for (x = first[q[l]]; x; x = e[x].next){
69             y = e[x].to;
70             if (d[q[l]] + e[x].cost < d[y] && e[x].f){
71                 d[y] = d[q[l]] + e[x].cost;
72                 g[y] = x;
73                 if (!v[y])
74                     q[++r] = y, v[y] = 1;
75             }
76         }
77         v[q[l]] = 0;
78     }
79     return d[T] != inf;
80 }
81   
82 int main(){
83     n = read(), m = read(), s = read();
84     S = n + 1, T = n + 2;
85     for (int i = 1; i <= n; ++i)
86         add_Edges(i, T, read(), 0);
87     for (int i = 1; i <= n; ++i)
88         add_Edges(S, i, inf, read());
89     for (int i = 1; i < n; ++i)
90         add_Edges(i, i + 1, s, m);
91     while (spfa())
92         ans += calc() * d[T];
93     printf("%d\n", ans);
94     return 0;
95 }
View Code

 

posted on 2015-03-17 19:51  Xs酱~  阅读(211)  评论(0)  编辑  收藏  举报