adding geeks for geeks algorithm

src/geeksforgeeks/algorithm.py

+'''
+Created on Feb 26, 2021
+
+@author: ARI
+'''
+def lcs(X , Y): 
+    # find the length of the strings 
+    m = len(X) 
+    n = len(Y) 
+  
+    # declaring the array for storing the dp values 
+    L = [[None]*(n+1) for i in range(m+1)] 
+  
+    """Following steps build L[m+1][n+1] in bottom up fashion 
+    Note: L[i][j] contains length of LCS of X[0..i-1] 
+    and Y[0..j-1]"""
+    for i in range(m+1): 
+        for j in range(n+1): 
+            if i == 0 or j == 0 : 
+                L[i][j] = 0
+            elif X[i-1] == Y[j-1]: 
+                L[i][j] = L[i-1][j-1]+1
+            else: 
+                L[i][j] = max(L[i-1][j] , L[i][j-1]) 
+  
+    # L[m][n] contains the length of LCS of X[0..n-1] & Y[0..m-1] 
+    return L[m][n] 
+#end of function lcs
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