{"id":33552,"date":"2024-11-01T09:17:44","date_gmt":"2024-11-01T09:17:44","guid":{"rendered":"http:\/\/atmokpo.com\/w\/?p=33552"},"modified":"2024-11-01T11:38:00","modified_gmt":"2024-11-01T11:38:00","slug":"java-coding-test-course-hacking-efficiently","status":"publish","type":"post","link":"https:\/\/atmokpo.com\/w\/33552\/","title":{"rendered":"Java Coding Test Course, Hacking Efficiently"},"content":{"rendered":"

<\/p>\n

Hello! Today, I solved algorithm problems through a coding test course using Java. In particular, I will introduce a problem related to ‘hacking’ and explain the process of solving it step by step. This course is aimed at those who primarily use the Java language and includes content designed to enhance algorithm problem-solving skills.<\/p>\n

Problem Description<\/h2>\n

Problem Title: Hacker’s Password<\/strong><\/p>\n

The hacker is trying to discover the password to break into a small company’s server. Luckily, the hacker knows a series of previous passwords. These passwords consist of different alphabet characters. The hacker must identify the ‘most frequently used alphabet’ to guess the password.<\/p>\n

Problem Definition<\/h3>\n
\nInput: \n- N (1 \u2264 N \u2264 1000): Number of passwords\n- Password: Maximum length of 50, consisting only of lowercase alphabet letters.\n\nOutput: \nPrint the most frequently used alphabet and its count in the format \"alphabet: count\".\n<\/pre>\n
Example Input<\/h3>\n
\n5\nabcde\nfghij\nklmno\nabcfg\nhijkl\n<\/pre>\n
Example Output<\/h3>\n
\na: 2\nb: 2\nc: 2\nf: 2\ng: 2\nh: 2\ni: 2\nj: 2\nk: 2\nl: 2\nm: 1\nn: 1\no: 1\n<\/pre>\n
Problem Solving Approach<\/h2>\n
To solve this problem, I considered the following approach.<\/p>\n
Step 1: Understand and Analyze the Problem<\/h3>\n
The given problem is to count the frequency of alphabets appearing in each password and print the most frequently occurring alphabet. Considering the number of inputs and the characteristics of each password, this problem is algorithmically suitable for the Counting<\/strong> method. By counting, we can implement a structure to count the frequency of each alphabet.<\/p>\n
Step 2: Design Data Structure<\/h3>\n
We will use a HashMap<\/code> to store the frequency of alphabets. The HashMap stores data as key-value pairs, where the key is the alphabet character (‘a’~’z’) and the value is the frequency of that alphabet. This structure allows us to traverse through each password and calculate the frequency.<\/p>\n
Step 3: Design Algorithm<\/h3>\n
\n1. Create a HashMap to store the count of alphabets.\n2. Traverse through the given passwords.\n3. For each password, traverse again and count the alphabets.\n4. Output the results in the following format: \"alphabet: count\".\n<\/pre>\n
Java Code Implementation<\/h2>\n
Now that the algorithm is established, let’s implement it in Java code.<\/p>\n
\nimport java.util.HashMap;\nimport java.util.Map;\nimport java.util.Scanner;\n\npublic class HackerPassword {\n    public static void main(String[] args) {\n        Scanner scanner = new Scanner(System.in);\n        int n = scanner.nextInt();\n        scanner.nextLine(); \/\/ Clear buffer\n\n        Map frequencyMap = new HashMap<>();\n        \n        \/\/ Input passwords and counting\n        for (int i = 0; i < n; i++) {\n            String password = scanner.nextLine();\n            for (char c : password.toCharArray()) {\n                frequencyMap.put(c, frequencyMap.getOrDefault(c, 0) + 1);\n            }\n        }\n\n        \/\/ Output results\n        for (Map.Entry entry : frequencyMap.entrySet()) {\n            System.out.println(entry.getKey() + \": \" + entry.getValue());\n        }\n    }\n}\n<\/code><\/pre>\n
Code Explanation<\/h2>\n
Let\u2019s look at the code step by step:<\/p>\n