# 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