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Longest Common Prefix

 Write a function to find the longest common prefix string amongst an array of strings.

If there is no common prefix, return an empty string "" .

Example: 

input : [ "flower" , "flow" , "flight" ]

output : fl


input : [ "dog" , "racecar" , "car" ] 

output : ""   (empty string)


Java

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 public class LongestCommonPrefix{
     public static void main(String []args){
        String[] arr = { "flower", "flow", "flight" };
        String result = findLongestCommonPrefix(arr);
        System.out.print(result);
     }
     public static String findLongestCommonPrefix(String[] arr){
         String lcp = "";     // longest common prefix
         int index = 0; 
         if(arr==null || arr.length==0)
            return lcp;
         for(char c : arr[0].toCharArray()){
             for(int i=1; i<arr.length; i++){
                 if( index >= arr[i].length() || c != arr[i].charAt(index) )
                    return lcp;
             }
             lcp += c ;
             index++;
         }
         return lcp;
     }
 }



Python

def findLongestCommonPrefix(arr):
    lcp = ""  # longest common prefix
    index = 0
    if(arr == None or len(arr)==0):
        return lcp
    for c in arr[0]:
        for word in arr:
            if index > len(word) or c != word[index]:
                return lcp
        lcp += c
        index += 1
    return lcp
    
arr = [ "flower", "flow", "flight"]
print(findLongestCommonPrefix(arr))

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