137. Single Number II
Posted Updated LeetCode / Meiduma few seconds read (About 102 words)

137. Single Number II

Question

Given an integer array nums where every element appears three times except for one, which appears exactly once. Find the single element and return it.

You must implement a solution with a linear runtime complexity and use only constant extra space.

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Posted Updated LeetCode / Medium2 minutes read (About 359 words)

609. Find Duplicate File in System

Question

Given a list paths of directory info, including the directory path, and all the files with contents in this directory, return all the duplicate files in the file system in terms of their paths. You may return the answer in any order.

A group of duplicate files consists of at least two files that have the same content.

A single directory info string in the input list has the following format:

  • "root/d1/d2/.../dm f1.txt(f1_content) f2.txt(f2_content) ... fn.txt(fn_content)"

It means there are n files (f1.txt, f2.txt ... fn.txt) with content (f1_content, f2_content ... fn_content) respectively in the directory “root/d1/d2/.../dm". Note that n >= 1 and m >= 0. If m = 0, it means the directory is just the root directory.

The output is a list of groups of duplicate file paths. For each group, it contains all the file paths of the files that have the same content. A file path is a string that has the following format:

  • "directory_path/file_name.txt"

Solution

使用StringBuffer对字符串进行处理。
采用HashMap建立内容和对应列表的映射。

遍历处理字符串，并添加到map中。
最后遍历map，如果对应的列表size大于1，则加入结果。

Code

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class Solution {
    public List<List<String>> findDuplicate(String[] paths) {
        List<List<String>> res = new ArrayList<>();
        HashMap<String, List<String>> map = new HashMap<>();
        
        for(String path : paths){
            StringBuffer folder = new StringBuffer();
            
            int i = 0;
            while(path.charAt(i) != ' '){
                folder.append(path.charAt(i));
                i++;
            }
            while(i < path.length()){
                while(path.charAt(i) == ' ') i++;
                StringBuffer filename = new StringBuffer();
                while(i < path.length() && path.charAt(i) != '('){
                    filename.append(path.charAt(i));
                    i++;
                }

                StringBuffer content = new StringBuffer();
                while(i < path.length() && path.charAt(i) != ')'){
                    content.append(path.charAt(i));
                    i++;
                }
                i++;
                List<String> arr = map.getOrDefault(content.toString(), new ArrayList<String>());
                arr.add(folder.toString() + '/' + filename);
                map.put(content.toString(), arr);
            }
        }
        
        for(String content : map.keySet()){
            if(map.get(content).size() > 1) res.add(map.get(content));
        }
        
        return res;
    }
}
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