review hanoi problem more expilicty than before
 median of median of five partationing for quick select Kth element has been solved!
 review median of median of five partationing ; each part is more explicity than before
 primary file completed ! need to modify later !!
Merge branch 'distist-point-pair' into divide-conquer

this merge action is not necessary, just a habbit
 cycle competation table (review later)
 will be finished tomorrow! just little bug ; before file is correct
 cycle-competataion is a better method to do it. and table-of-competation is another version of before, in fact, the before is good enough  and the last is not finsihed . if it must be finished. its method is the same as before
Merge branch 'cycle-competation-table' into divide-conquer

i spent a amount of time to rebuild a new method to finished it. but at last i failed. when i review the before file, its better than i firstly saw it. so there is no need to write a new file, think a new method to do it. use the before method is well
 nothing done !
in dynamic programming, more shkills needed, and these are the base problems should abtain
 small changes about optimal_bst and add new file sum2.c
debug some code