Time complexity of isRotation algorithm

Question

This common code is said to run in O(N) time assuming isSubstring runs in O(N+M) time. How do we get O(N) time complexity from this? public static boolean isRotation(String s1, String s2) { int len = s1.length(); if (len == s2.length() && len > 0) { String s1s1 = s1 + s1; return isSubstring(s1s1, s2); } return false; } JavaScript questions and answers, JavaScript questions pdf, JavaScript question bank, JavaScript questions and answers pdf, mcq on JavaScript pdf, JavaScript questions and solutions, JavaScript mcq Test , Interview JavaScript questions, JavaScript Questions for Interview, JavaScript MCQ (Multiple Choice Questions)

Answer 1

Usually when we say linear it means that with really really big number of basic operations our algorithm still performs in O(n). According to time complexity calculation of sublinear function like O(n+m) complexity gets pretty randomized but behaves like linear with large N. So generally we can say O(n)~O(n+m).