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

/**************************************************************
    Problem: 2424
    User: rausen
    Language: C++
    Result: Accepted
    Time:0 ms
    Memory:1028 kb
****************************************************************/
 
#include <cstdio>
#include <algorithm>
  
using namespace std;
const int inf = (int) 1e9;
const int N = 2005;
const int M = 10005;
struct edges{
    int next, to, cost, f;
} e[M];
int tot = 1, n, m, s;
int first[N], d[N], g[N], q[M];
bool v[N];
int S, T, ans;
  
inline int read(){
    int x = 0, sgn = 1;
    char ch = getchar();
    while (ch < '0' || ch > '9'){
        if (ch == '-') sgn = -1;
        ch = getchar();
    }
    while (ch >= '0' && ch <= '9'){
        x = x * 10 + ch - '0';
        ch = getchar();
    }
    return sgn * x;
}
  
inline void add_edge(int x, int y, int d, int c){
    e[++tot].next = first[x];
    first[x] = tot;
    e[tot].to = y;
    e[tot].f = d;
    e[tot].cost = c;
}
   
void add_Edges(int x, int y,int d, int c){
    add_edge(x, y, d, c);
    add_edge(y, x, 0, -c);
}
   
inline int calc(){
    int flow = inf;
    for (int x = g[T]; x; x = g[e[x ^ 1].to])
        flow = min(flow, e[x].f);
    for (int x = g[T]; x; x = g[e[x ^ 1].to])
        e[x].f -= flow, e[x ^ 1].f += flow;
    return flow;
}
   
bool spfa(){
    for (int i = 1; i <= T; ++i)
        d[i] = inf;
    d[S] = 0, v[S] = 1;
    q[1] = S;
    int x, y;
    for(int l = 1, r = 1; l <= r; ++l){
        for (x = first[q[l]]; x; x = e[x].next){
            y = e[x].to;
            if (d[q[l]] + e[x].cost < d[y] && e[x].f){
                d[y] = d[q[l]] + e[x].cost;
                g[y] = x;
                if (!v[y])
                    q[++r] = y, v[y] = 1;
            }
        }
        v[q[l]] = 0;
    }
    return d[T] != inf;
}
  
int main(){
    n = read(), m = read(), s = read();
    S = n + 1, T = n + 2;
    for (int i = 1; i <= n; ++i)
        add_Edges(i, T, read(), 0);
    for (int i = 1; i <= n; ++i)
        add_Edges(S, i, inf, read());
    for (int i = 1; i < n; ++i)
        add_Edges(i, i + 1, s, m);
    while (spfa())
        ans += calc() * d[T];
    printf("%d
", ans);
    return 0;
}