Theory Depth-first search (DFS) is an algorithm for traversing or searching graph or tree 🎄 data structures. The algorithm starts at the root node (selecting some arbitrary node as the root node in the case of a graph) and explores as far as possible along each branch before backtracking.

Theory Dynamic programming is both a mathematical optimization method and a computer programming method. The method was developed by Richard Bellman🧐 in the 1950s and has found applications in numerous fields, from aerospace engineering to economics.

Using + When one of the left and right variables is of type String, the plus method can be used to convert the two variables into strings and concatenate them.

Using split() Pass the regular into split(). The return is a String[] type. However, intercepting in this way will have a large performance penalty, because analyzing the regularity is very time-consuming.