UVA 11478 Halum

写的好搓啊。。新年第一水。

View Code 
  1 #include <iostream>
  2 #include <cstdio>
  3 #include <cstring>
  4 #include <queue>
  5 #define maxn 510
  6 #define maxm 2710
  7 using namespace std;
  8 int v[maxm],w[maxm],next[maxm];
  9 int first[maxn],inq[maxn],cnt[maxn],d[maxn];
 10 int e,V,E;
 11 
 12 void init()
 13 {
 14     memset(first,-1,sizeof(first));
 15     memset(next,0,sizeof(next));
 16 }
 17 
 18 void Read_Graph()
 19 {
 20     int a,b,c;
 21     e = 0;
 22     for(int i = 0;i < E;i++)
 23     {
 24         scanf("%d%d%d",&a,&b,&c);
 25         v[e] = b;
 26         next[e] = first[a];
 27         first[a] = e;
 28         w[e] = c;
 29         e++;
 30     }
 31 }
 32 
 33 bool negativeCycle()
 34 {
 35     queue<int> q;
 36     memset(cnt,0,sizeof(cnt));
 37     memset(inq,0,sizeof(inq));
 38     int i;
 39     for(i = 1;i <= V;i++)
 40     {
 41         d[i] = 0;
 42         q.push(i);
 43     }
 44 
 45     inq[1] = 1;
 46 
 47     while(!q.empty())
 48     {
 49         int ith = q.front();
 50         q.pop();
 51         inq[ith] = 0;
 52         for(i = first[ith];i != -1;i = next[i])
 53         {
 54             if(d[v[i]] > d[ith] + w[i])
 55             {
 56                 d[v[i]] = d[ith] + w[i];
 57                 if(!inq[v[i]])
 58                 {
 59                     inq[v[i]] = 1;
 60                     q.push(v[i]);
 61                     if(++cnt[v[i]] > V) return true;
 62                 }
 63             }
 64         }
 65     }
 66     return false;
 67 }
 68 
 69 bool test(int x)
 70 {
 71     int i;
 72     bool ret;
 73     for(i = 0;i < e;i++)
 74         w[i] -= x;
 75     ret = negativeCycle();
 76     for(i = 0;i < e;i++)
 77         w[i] += x;
 78     return ret;
 79 }
 80 
 81 void solve()
 82 {
 83     if(test(0))
 84     {
 85         printf("No Solution\n");
 86         return;
 87     }
 88     if(!test(10001))
 89     {
 90         printf("Infinite\n");
 91         return;
 92     }
 93     int l = 1,r = 10000,mid;
 94     while(l < r)
 95     {
 96         mid = (l + r) >> 1;
 97         if(test(mid))   r = mid;
 98         else            l = mid + 1;
 99     }
100     l--;
101     if(l == 0)  printf("No Solution\n");
102     else    printf("%d\n",l);
103 }
104 int main()
105 {
106     while(scanf("%d%d",&V,&E) == 2)
107     {
108         init();
109         Read_Graph();
110         solve();
111     }
112     return 0;
113 }

 

posted @ 2013-01-01 20:34  浙西贫农  阅读(153)  评论(0)  编辑  收藏  举报