算法难，递归易，算法皆以递归源，相同处理自循环；

递归处理分和并，分而治之是首选。

DP全，贪心简，最优性质二者兼；

DP需要表来填，子问题解表中见；

贪心策略需证明，整体可由局部建。

回溯深，分限广，剪枝函数两边忙；

一边剪左不可行，一边剪右非最优。

分限还需优先级，上界下界来排序；

叶子放在队列里，轮到它时达目的。-Algorithm is difficult, recursive easy recursive algorithm begin with the source, the same treatment from the cycle　recursive processing points, and, of divide and rule is preferred. DP Quan, greed Jane, the optimal nature of the two chief　DP need to fill in the table, sub-problem solution in the table, see　greedy strategy will need to prove that the whole can be built locally. Back deep, sub-limit of a wide pruning function on both sides of busy　the left side of the cut is not feasible, cut the right side of the non-optimal. Sub-limit needed priority, the upper bound lower bound to sort　leaves placed in the queue, the turn when it attain this purpose.