leetcode 636. Exclusive Time of Functions 函数的单独运行时间 + stringstream很好应用
GiventherunninglogsofnfunctionsthatareexecutedinanonpreemptivesinglethreadedCPU,findtheexclusivetimeofthesefunctions.Eachfunctionhasauniqueid,startfrom0ton-1.Afunctionmaybecalledrecursivelyorbyanother