按扩展名的字典顺序对文件名进行排序

给定一个字符串数组Files[] ，代表一些文件的名称，任务是根据文件名扩展名的字典顺序对数组进行排序。如果多个文件具有相同的扩展名，则按字典顺序对它们进行排序。

例子：

Input: files[] = {“ajay.cpp”, “pchy.pdf”, “loki.docx”, “raju.zip” } 
Output: ajay.cpp, loki.docx, pchy.pdf, raju.zip 
Explanation: 
Lexicographically sorted order of “cpp” < “docx” < “pdf” < “zip”

Input: files[] = {“abc.cpp”, “bcd.cpp”, “ab.cpp”, “efg.zip”} 
Output: ab.cpp, abc.cpp, bcd.cpp, efg.zip 
Explanation: 
Since the file names { “abc.cpp”, “bcd.cpp”, “ab.cpp” } have same extension, they are sorted lexicographical order of their names. 
 

处理方法：按照以下步骤解决问题：

• 使用比较器函数根据扩展名对字符串数组进行排序。
• 对于任何一对具有相同扩展名的文件，按名称的字典顺序对它们进行排序。
• 最后，打印字符串数组。

下面是上述方法的实现：

C++

// C++ Program for the above approach
 
#include 
using namespace std;
 
// Comparator function to sort an array of strings
// based on the extension of their file names
bool custom(string s1, string s2)
{
 
    // Stores index of '.' in s1
    size_t i = s1.find('.');
 
    // Stores index of '.' in s2
    size_t j = s2.find('.');
 
    // Stores name of extension of s2
    string d = s1.substr(i + 1);
 
    // Stores name of extension of s2
    string e = s2.substr(j + 1);
 
    // If both files have the
    // same extension name
    if (d == e) {
 
        // Return lexicographically
        // smaller of the two strings
        return s1 < s2;
    }
 
    return d < e;
}
 
// Function to sort the files names
// based on the name of their extension
void sortfromextension(vector& files)
{
 
    // Sort file names in lexicographical
    // order of their extensions
    sort(files.begin(), files.end(), custom);
 
    // Print files in sorted form
    // based on extension names
    for (auto s : files) {
        cout << s << ", ";
    }
}
 
// Driver Code
int main()
{
    vector files
        = { "ajay.cpp", "pchy.pdf",
            "loki.docx", "raju.zip" };
 
    sortfromextension(files);
    return 0;
}

Java

// Java program for above approach
import java.util.*;
import java.lang.*;
class GFG
{
 
  // Function to sort the files names
  // based on the name of their extension
  static void sortfromextension(String[] files)
  {
 
    // Sort file names in lexicographical
    // order of their extensions
    Arrays.sort(files, new Comparator(){
 
      public int compare(String s1,String s2){
 
        // Stores index of '.' in s1
        int i = s1.indexOf('.');
 
        // Stores index of '.' in s2
        int j = s2.indexOf('.');
 
        // Stores name of extension of s2
        String d = s1.substring(i + 1);
 
        // Stores name of extension of s2
        String e = s2.substring(j + 1);  
        return (d.equals(e))?(s1.compareTo(s2)<0?-1:1):(d.compareTo(e)<0?-1:1);
      }
 
    });
 
    // Print files in sorted form
    // based on extension names
    for (int i = 0; i < files.length - 1; i++)
    {
      System.out.print(files[i] + ", ");
    }
    System.out.print(files[files.length - 1]);
  }
  // Driver function
  public static void main (String[] args)
  {
    String[] files
      = { "ajay.cpp", "pchy.pdf",
         "loki.docx", "raju.zip" };
 
    sortfromextension(files);
  }
}
 
// This code is contributed by offbeat

输出

ajay.cpp, loki.docx, pchy.pdf, raju.zip, 

时间复杂度： O(N * log(N))
辅助空间： O(1)

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