What is the best place OR How to learn time complexity by examples like below code.\nI understand simple loops but feel difficult in little difficult code.\n```\n\tpublic int dfs(string w, int depth, HashSet<string> set){\n        int max = depth;\n        for(int j=0;j<w.Length;j++){\n            string b = w.Substring(0,j) + w.Substring(j+1);\n            if(set.Contains(b)){\n                set.Remove(b);\n                max = Math.Max(max, dfs(b, depth+1, set));\n            }\n        }\n        \n        return max;\n    }

What is the best place OR How to learn time complexity by examples like below code.\nI understand simple loops but feel difficult in little difficult code.\n```