解题：SCOI 2011 糖果

题面

能把差分约束卡死的题，因为正解并不是差分约束

 1 #include<queue>
 2 #include<cstdio>
 3 #include<cctype>
 4 #include<cstring>
 5 #include<algorithm>
 6 using namespace std;
 7 const int N=100005;
 8 int p[N],noww[2*N],goal[2*N],val[2*N];
 9 int vis[N],inq[N],dis[N];
10 int n,k,t1,t2,t3,cnt;
11 long long ans;
12 queue<int> qs;
13 inline int read()
14 {
15     int ret=0;
16     char ch=getchar();
17     while(!isdigit(ch))
18         ch=getchar();
19     while(isdigit(ch))
20         ret=(ret<<3)+(ret<<1)+(ch^48),ch=getchar();
21     return ret;
22 }
23 inline void link(int f,int t,int v)
24 {
25     noww[++cnt]=p[f],p[f]=cnt;
26     goal[cnt]=t,val[cnt]=v;
27 }
28 void SBData()
29 {
30     if((t1==2||t1==4)&&t2==t3)
31         {printf("-1"); exit(0);}
32 }
33 int main ()
34 {
35     register int i;
36     n=read(),k=read();
37     for(i=1;i<=k;i++)
38     {
39         t1=read(),t2=read(),t3=read();
40         if(t1==1) link(t2,t3,0),link(t3,t2,0);
41         else if(t1==2) link(t2,t3,1);
42         else if(t1==3) link(t3,t2,0);
43         else if(t1==4) link(t3,t2,1);
44         else link(t2,t3,0); SBData();
45     }
46     for(i=1;i<=n;i++)
47         qs.push(i),dis[i]=vis[i]=1,inq[i]=true;
48     while(!qs.empty())
49     {
50         int tn=qs.front();
51         qs.pop(),inq[tn]=false;
52         for(i=p[tn];i;i=noww[i])
53             if(dis[goal[i]]<dis[tn]+val[i])
54             {
55                 dis[goal[i]]=dis[tn]+val[i];
56                 if(!inq[goal[i]])
57                 {
58                     if(++vis[goal[i]]>n) {printf("-1"); return 0;}
59                     qs.push(goal[i]),inq[goal[i]]=true;
60                 }
61             }
62     }
63     for(i=1;i<=n;i++) ans+=dis[i];
64     printf("%lld",ans);
65     return 0;
66 }

原文地址：https://www.cnblogs.com/ydnhaha/p/9726870.html