hdu 4274 2012长春赛区网络赛 树形dp ***

设定每个节点的上限和下限，之后向上更新，判断是否出现矛盾

 #include<cstdio>
 #include<iostream>
 #include<algorithm>
 #include<cstring>
 #include<cmath>
 #include<queue>
 #include<map>
 using namespace std;
 #define MOD 1000000007
 const int INF=;
 const double eps=1e-;
 typedef long long ll;
 #define cl(a) memset(a,0,sizeof(a))
 #define ts printf("*****\n");
 const int N=;
 int n,m,tt,tot=,head[N],dp[N];
 int maxw;
 bool flag;
 struct edge
 {
     int to,next;
 }edge[N*];
 int up[N],low[N];
 void addedge(int a,int b)
 {
     edge[tot].to=a;
     edge[tot].next=head[b];
     head[b]=tot++;
 }
 void init()
 {
     memset(head,-,sizeof(head));
     tot=;
 }
 void dfs(int u,int pre)
 {
     if(flag)    return;
     if(up[u]!=-&&low[u]>up[u])
     {
         flag=;
         return;
     }
     int le=;
     int sum=;
     for(int i=head[u];i!=-;i=edge[i].next)
     {
         int v=edge[i].to;
         if(v==pre)  continue;
         le=;
         dfs(v,u);
         sum+=low[v];
     }
     if(!le)   return;
     low[u]=max(sum+,low[u]);
     if(up[u]!=-&&low[u]>up[u])
     {
         flag=;
         return;
     }
 }
 int main()
 {
     int i,j,k;
     #ifndef ONLINE_JUDGE
     freopen("1.in","r",stdin);
     #endif
     while(scanf("%d",&n)!=EOF)
     {
         init();
         for(i=;i<=n;i++)
         {
             int u;
             scanf("%d",&u);
             addedge(i,u);
             addedge(u,i);
         }
         for(i=;i<=n;i++)    up[i]=-,low[i]=;
         scanf("%d",&m);
         for(i=;i<m;i++)
         {
             int u,v,w;
             char c[];
             scanf("%d%s%d",&u,c,&w);
             if(c[]=='<')  up[u]=w-;
             else if(c[]=='>')  low[u]=w+;
             else low[u]=up[u]=w;
         }
         flag=;
         dfs(,-);
         if(flag)
         {
             printf("Lie\n");
         }
         else    printf("True\n");
     }
 }