BZOJ2055 80人环游世界

m个人随便设定起点= =，所以是有上下界网络流喽、、、

今天刚学，于是试着写了写，1A耶！

费用流是板子哦~

 

  1 /**************************************************************
  2     Problem: 2055
  3     User: rausen
  4     Language: C++
  5     Result: Accepted
  6     Time:536 ms
  7     Memory:8624 kb
  8 ****************************************************************/
  9  
 10 #include <cstdio>
 11 #include <algorithm>
 12  
 13 using namespace std;
 14 const int inf = (int) 1e9;
 15 const int N = 205;
 16 const int M = 500005;
 17  
 18 struct edges{
 19     int next, to, f, cost;
 20     edges() {}
 21     edges(int _next, int _to, int _f, int _cost) : next(_next), to(_to), f(_f), cost(_cost) {}
 22 } e[M];
 23   
 24 int n, m, tot = 1;
 25 int first[N], Del[N], d[N], g[N];
 26 bool v[N];
 27 int q[N], l, r;
 28 int S, S1, T;
 29  
 30 inline int read() {
 31     int x = 0, sgn = 1;
 32     char ch = getchar();
 33     while (ch < '0' || '9' < ch) {
 34         if (ch == '-') sgn = -1;
 35         ch = getchar();
 36     }
 37     while ('0' <= ch && ch <= '9') {
 38         x = x * 10 + ch - '0';
 39         ch = getchar();
 40     }
 41     return sgn * x;
 42 }
 43  
 44 inline void add_edge(int x, int y, int f, int c) {
 45     e[++tot] = edges(first[x], y, f, c);
 46     first[x] = tot;
 47 }
 48   
 49 void Add_Edges(int x, int y, int f, int c) {
 50     add_edge(x, y, f, c);
 51     add_edge(y, x, 0, -c);
 52 }
 53   
 54 inline int calc() {
 55     int flow = inf, x;
 56     for (x = g[T]; x; x = g[e[x ^ 1].to])
 57         flow = min(flow, e[x].f);
 58     for (x = g[T]; x; x = g[e[x ^ 1].to])
 59         e[x].f -= flow, e[x ^ 1].f += flow;
 60     return flow;
 61 }
 62   
 63 bool spfa() {
 64     int x, y;
 65     for (x = 1; x <= T; ++x)
 66         d[x] = inf;
 67     d[S] = 0, v[S] = 1, q[0] = S;
 68     for(l = r = 0; l != (r + 1) % N; ++l %= N) {
 69         for (x = first[q[l]]; x; x = e[x].next)
 70             if (d[q[l]] + e[x].cost < d[y = e[x].to] && e[x].f) {
 71                 d[y] = d[q[l]] + e[x].cost;
 72                 g[y] = x;
 73                 if (!v[y])
 74                     q[++r %= N] = y, v[y] = 1;
 75             }
 76         v[q[l]] = 0;
 77     }
 78     return d[T] != inf;
 79 }
 80  
 81 inline int work() {
 82     int res = 0;
 83     while (spfa())
 84         res += calc() * d[T];
 85     return res;
 86 }
 87  
 88 int main() {
 89     int i, j, x;
 90     n = read(), m = read();
 91     S = n * 2 + 1, S1 = n * 2 + 2, T = n * 2 + 3;
 92     for (i = 1; i <= n; ++i) {
 93         x = read();
 94         Add_Edges(i, i + n, 0, 0);
 95         Del[i] -= x, Del[i + n] += x;
 96     }
 97     Add_Edges(S, S1, m, 0);
 98     for (i = 1; i <= n; ++i)
 99         Add_Edges(S1 ,i, inf, 0);
100     for (i = 1; i <= n; ++i)
101         for (j = i + 1; j <= n; ++j)
102             if ((x = read()) != -1)
103                 Add_Edges(i + n, j, inf, x);
104     for (i = 1; i <= n * 2; ++i)
105         if (Del[i] > 0) Add_Edges(S, i, Del[i], 0);
106         else Add_Edges(i, T, -Del[i], 0);
107     printf("%d\n", work());
108     return 0;
109 }
View Code

 

posted on 2014-11-18 18:44  Xs酱~  阅读(210)  评论(0)  编辑  收藏  举报