add rob doc

tg123 · tg123 · commit 9bcbf36a7d80 · 2015-03-31T20:10:39.000+08:00
diff --git a/house-robber/README.md b/house-robber/README.md
@@ -0,0 +1,33 @@
+## Rob or not
+
+assume that there are 9 houses along the street
+and you have a `rob` func can tell you the how much money you can get from first 8 hourses.
+
+
+what about the 9th house
+
+```
+?  = not sure
+*  = must rob
+_  = must not rob
+
+rob
+
+[? ? ? ? ? ? ? ?] _ *
+[0 1 2 3 4 5 6 7] 8 9
+
+money = rob(0..7) + house_value[9]
+
+or not
+
+[? ? ? ? ? ? ? ? ?] _
+[0 1 2 3 4 5 6 7 8] 9
+
+money = rob(0..8)
+
+
+rob(0..9) = max(rob(0..8), rob(0..7) + house_value[9])
+```
+
+then it is easy to write a `rob(0..n)`
+
