From b0112b27756b853c0f6400ee475aa31180814ddf Mon Sep 17 00:00:00 2001
From: HarshaK1302 <72301516+HarshaK1302@users.noreply.github.com>
Date: Tue, 6 Oct 2020 13:06:26 +0530
Subject: [PATCH] Create longestCommonSubsequence.py

add this
---
 longestCommonSubsequence.py | 43 +++++++++++++++++++++++++++++++++++++
 1 file changed, 43 insertions(+)
 create mode 100644 longestCommonSubsequence.py

diff --git a/longestCommonSubsequence.py b/longestCommonSubsequence.py
new file mode 100644
index 0000000..9e760e9
--- /dev/null
+++ b/longestCommonSubsequence.py
@@ -0,0 +1,43 @@
+
+def lcs(u, v):
+   
+    c = [[-1]*(len(v) + 1) for _ in range(len(u) + 1)]
+    lcs_helper(u, v, c, 0, 0)
+    return c
+ 
+ 
+def lcs_helper(u, v, c, i, j):
+   
+    if c[i][j] >= 0:
+        return c[i][j]
+ 
+    if i == len(u) or j == len(v):
+        q = 0
+    else:
+        if u[i] == v[j]:
+            q = 1 + lcs_helper(u, v, c, i + 1, j + 1)
+        else:
+            q = max(lcs_helper(u, v, c, i + 1, j),
+                    lcs_helper(u, v, c, i, j + 1))
+    c[i][j] = q
+    return q
+ 
+ 
+def print_lcs(u, v, c):
+    i = j = 0
+    while not (i == len(u) or j == len(v)):
+        if u[i] == v[j]:
+            print(u[i], end='')
+            i += 1
+            j += 1
+        elif c[i][j + 1] > c[i + 1][j]:
+            j += 1
+        else:
+            i += 1
+ 
+ 
+u = input('Enter first string: ')
+v = input('Enter second string: ')
+c = lcs(u, v)
+print('Longest Common Subsequence: ', end='')
+print_lcs(u, v, c)