最大子序列和的求法，c++代码次优和最优实现，次优算法MaxSubsequenceSum3采用递归O(Nlog(N))，最优算法MaxSubsequenceSum4是一种联机算法,O(N)-Sequence and the largest Method, c++ code, sub-optimal and optimal implementation, sub-optimal algorithm MaxSubsequenceSum3 recursively O (Nlog (N)), optim