strings: add longest_common_prefix algorithm with doctests

Author: sindz22

strings/longest_common_prefix.py

@@ -0,0 +1,48 @@
+def longest_common_prefix(strs: list[str])->str:
+    """
+    :type strs: List[str]
+    
+    Args:
+        strs (list[str]): A list of strings.
+
+
+    Returns:
+        str:The longest common prefix shared among all strings.
+            Returns an empty string if there is none.
+    
+    Test cases:
+    >>> longest_common_prefix(["flower","flow","flap"])
+    'fl'
+    >>> longest_common_prefix(["cats","dragon","dracula"])
+    ''
+    >>> longest_common_prefix(["marianne","mariachi"])
+    'maria'
+    >>> longest_common_prefix([])
+    ''
+    >>> longest_common_prefix(["","belly","belt"])
+    ''
+    >>> longest_common_prefix(["#hashtag","#hashbrown","#hash"])
+    '#hash'
+    """
+    ans=""
+    if not strs:
+        return ""
+    if len(strs)==1:
+        return strs[0]
+    
+    k=0
+    ref=strs[0]
+
+    while k<len(ref):
+        for ele in strs:
+            if len(ele)<k+1 or ref[k]!=ele[k]:  
+
+                return ans
+        ans+=ele[k]
+        k+=1
+    return ans
+
+
+                
+
+