HDU 1224 - Free DIY Tour
Problem : Given a DAG, each vertice has a fun value a[i]. Find a path from source to destination, such that the sum of visited verices' fun value is maximum.
Solution : RAW DAG DP. f[u] is the maximum value from source to u. Then f[u]=max(f[v])+a[u], where v is the vertices s.t. there is an edge v->u.