【算法设计与分析作业题】第九周：17. Letter Combinations of a Phone Number
题目C++solutionclassSolution{public:vectorletterCombinations(stringdigits){vectorresult;if(digits.size()==0)//数字串为空串则直接返回空数组returnresult;vectorletters={"abc","def","ghi","jkl","mno","pqrs","tuv","wxyz"}