longest common substring

Author: sagivo

longest_common_substring.rb

@@ -0,0 +1,19 @@
+def LCSLength (x, y)
+    h = Array.new(x.size) {Array.new(y.size)}
+    x.size.times {|i| h[i][0] = x[0] == y[0] ? 1 : 0 }
+    y.size.times {|i| h[0][i] = x[0] == y[0] ? 1 : 0 }
+
+    (1..x.size-1).each do |i|
+        (1..y.size-1).each do |j|
+            if x[i] == y[j]
+                h[i][j] = (h[i-1][j-1] ? h[i-1][j-1] : 0) + 1
+            else
+                h[i][j] = [ h[i-1][j] ? h[i-1][j] : 0, h[i][j-1] ? h[i][j-1] : 0].max
+            end
+        end
+    end
+    h[x.size-1][y.size-1]
+end
+
+
+p LCSLength('waaaa', 'bbbbasfaaewra') #returns 4