easy prim
add poj3255 djs
Merge branch 'master' of https://github.com/LiaoPengyu/algorithm

* 'master' of https://github.com/LiaoPengyu/algorithm:
  add some algorithm
  add mergesort and heapsort
  add lca to rmq
  add a dp
  delete .# file
  add ignore rule
  add ignore
  delete #
  a dp
  chapter 3 and 4
  fix solution
  new solution, not O(lgn) for push and pop, O(1) for min
  add some code for coding interview
  rm dup code
  hdu1233 prim and kruskal