使用排序的最长公共前缀

问题陈述：给定一组字符串，找到最长的公共前缀。

例子：

Input: {"geeksforgeeks", "geeks", "geek", "geezer"}
Output: "gee"

Input: {"apple", "ape", "april"}
Output: "ap"

字符串数组的最长公共前缀是2个最不相似的字符串之间的公共前缀。例如，在给定的数组{“ apple”，“ ape”，“ zebra”}中，没有公共前缀，因为数组“ ape”和“ zebra”中两个最不相似的字符串不共享任何起始字符。

我们在以下帖子中讨论了五种不同的方法。

1. 逐字匹配
2. 逐匹配
3. 分而治之
4. 二进制搜索。
5. 使用特里)

在这篇文章中，讨论了一种基于排序的新方法。这个想法是对字符串数组进行排序，并找到已排序数组的第一个和最后一个字符串的公共前缀。

C++

// C++ program to find longest common prefix 
// of given array of words.
#include
#include
  
using namespace std;
  
// Function to find the longest common prefix
string longestCommonPrefix(string ar[], int n)
{
  
    // If size is 0, return empty string
    if (n == 0)
        return "";
  
    if (n == 1)
        return ar[0];
  
    // Sort the given array
    sort(ar, ar + n);
  
    // Find the minimum length from 
    // first and last string
    int en = min(ar[0].size(), 
                 ar[n - 1].size());
  
    // Now the common prefix in first and 
    // last string is the longest common prefix
    string first = ar[0], last = ar[n - 1];
    int i = 0;
    while (i < en && first[i] == last[i])
        i++;
  
    string pre = first.substr(0, i);
    return pre;
}
  
// Driver Code
int main()
{
    string ar[] = {"geeksforgeeks", "geeks", 
                           "geek", "geezer"};
    int n = sizeof(ar) / sizeof(ar[0]);
    cout << "The longest common prefix is: "
         << longestCommonPrefix(ar, n);
    return 0;
}
  
// This code is contributed by jrolofmeister

Java

// Java program to find longest common prefix of
// given array of words.
import java.util.*;
  
public class GFG
{
    public String longestCommonPrefix(String[] a)
    {
        int size = a.length;
  
        /* if size is 0, return empty string */
        if (size == 0)
            return "";
  
        if (size == 1)
            return a[0];
  
        /* sort the array of strings */
        Arrays.sort(a);
  
        /* find the minimum length from first and last string */
        int end = Math.min(a[0].length(), a[size-1].length());
  
        /* find the common prefix between the first and
           last string */
        int i = 0;
        while (i < end && a[0].charAt(i) == a[size-1].charAt(i) )
            i++;
  
        String pre = a[0].substring(0, i);
        return pre;
    }
  
    /* Driver Function to test other function */
    public static void main(String[] args)
    {
        GFG gfg = new GFG();
        String[] input = {"geeksforgeeks", "geeks", "geek", "geezer"};
        System.out.println( "The longest Common Prefix is : " +
                                   gfg.longestCommonPrefix(input));
    }
}

Python 3

# Python 3 program to find longest 
# common prefix of given array of words.
def longestCommonPrefix( a):
      
    size = len(a)
  
    # if size is 0, return empty string 
    if (size == 0):
        return ""
  
    if (size == 1):
        return a[0]
  
    # sort the array of strings 
    a.sort()
      
    # find the minimum length from 
    # first and last string 
    end = min(len(a[0]), len(a[size - 1]))
  
    # find the common prefix between 
    # the first and last string 
    i = 0
    while (i < end and 
           a[0][i] == a[size - 1][i]):
        i += 1
  
    pre = a[0][0: i]
    return pre
  
# Driver Code
if __name__ == "__main__":
  
    input = ["geeksforgeeks", "geeks", 
                     "geek", "geezer"]
    print("The longest Common Prefix is :" ,
                 longestCommonPrefix(input))
  
# This code is contributed by ita_c

C#

// C# program to find longest common prefix of
// given array of words.
using System;
          
public class GFG {
      
    static string longestCommonPrefix(String[] a)
    {
        int size = a.Length;
  
        /* if size is 0, return empty string */
        if (size == 0)
            return "";
  
        if (size == 1)
            return a[0];
  
        /* sort the array of strings */
        Array.Sort(a);
  
        /* find the minimum length from first
        and last string */
        int end = Math.Min(a[0].Length,
                            a[size-1].Length);
  
        /* find the common prefix between the 
        first and last string */
        int i = 0;
        while (i < end && a[0][i] == a[size-1][i] )
            i++;
  
        string pre = a[0].Substring(0, i);
        return pre;
    }
  
    /* Driver Function to test other function */
    public static void Main()
    {
          
        string[] input = {"geeksforgeeks", "geeks",
                                 "geek", "geezer"};
                                   
        Console.WriteLine( "The longest Common"
                              + " Prefix is : "
                  + longestCommonPrefix(input));
    }
}
  
// This code is contributed by Sam007.

输出：

The longest common prefix is : gee

时间复杂度： O(MAX * n * log n)，其中n是数组中的字符串数，MAX是任何字符串的最大字符数。请注意，比较两个字符串最多需要O(MAX)时间，而要对n个字符串进行排序，则需要O(MAX * n * log n)时间。