Longest Common Prefix in an Array

In n strings,  longest common prefix among all strings is to be found

Example 1:

Input:
n = 4
arr[] = {codemummy, code, codem,
         coder}
Output: code
Explanation: "code" is the longest common
prefix in all the given strings.

Example 2:

Input: 
n = 2
arr[] = {awesome, cris}
Output: -1
Explanation: There's no common prefix
in the given strings.

method 1 :

use sorting:

sort both the string now check if the sorted strings are equal if they are equal return 1, else return 0.

c++ implementation:

  string longestCommonPrefix (string a[], int n)
    {
        int l=a[0].length();
	    string result="-1"; 
        char current; 
	 
	  for(int i=0;i<l;i++)
	  {  current=a[0][i];
	     for(int j=1;j<n;j++)
	      { if(current!=a[j][i])
	          return result;
	      }
	      if(result=="-1")
	       result="";
	       result=result+current;
	  }
	  return result;
    }

Time Complexity: O(n*l) 

where n is the no. of strings and l is the length of first string