finish extra/fuel-injection-perfection

README.md

@@ -74,3 +74,5 @@ CFcSBwgCCBoHRhkKU1cGAA4AGU5YQR5THBwNFwoGGAxTQQMQVBUSBg4EAAwQRhUQVBUHFAQTGRpT QQM
 ### find-the-access-codes
 * Completed in: 1 hr, 6 mins, 52 secs.
 
+### fuel-injection-perfection
+* Completed in: 1 hr, 2 secs.

extra/fuel-injection-perfection/solution.py

@@ -0,0 +1,74 @@
+def solution(n):
+    # 1.  *0: /= 2
+    # 2. *01: -= 1
+    # 3. *11: += 1
+
+    # state 0: *0
+    # state 1: *1
+    # state 2: *11
+    result = 0
+    state = 0
+    count = 0
+    b = bin(int(n))[2:]
+    for c in bin(int(n))[:1:-1]:
+        if c == '0':
+            if state == 0: # 0*
+                count += 1
+            elif state == 1: # 01
+                result += 1 + 2 # remove one, divide by 2 twice
+                count = 0
+                state = 0 # .*01 => .*00 => .*
+            elif state == 2: # 01*
+                result += 1 + count # add one, divide by 2 count times
+                count = 1
+                state = 1 # .*01* => .*10* => .*1
+        if c == '1':
+            if state == 0: # 10*
+                result += count # divide by 2 count times
+                count = 1
+                state = 1 # .*10* => .*1
+            elif state == 1: # 11
+                count += 1
+                state = 2
+            elif state == 2: # 1*
+                count += 1
+    if state == 2: # 11*
+        if count == 2: # 11
+            result += 2
+        else:
+            result += 1 + count # add one, devide by 2 count times
+    return result
+
+
+tests = [
+        ('15', 5),
+        ('4', 2),
+        (str(int('1', 2)), 0),
+        (str(int('10', 2)), 1),
+        (str(int('11', 2)), 2),
+        (str(int('100', 2)), 2),
+        (str(int('101', 2)), 3),
+        (str(int('110', 2)), 3),
+        (str(int('111', 2)), 4),
+        (str(int('1000', 2)), 3),
+        (str(int('1001', 2)), 4),
+        (str(int('1010', 2)), 4),
+        (str(int('1011', 2)), 6),
+        (str(int('1100', 2)), 4),
+        (str(int('1101', 2)), 5),
+        (str(int('1110', 2)), 5),
+        (str(int('1111', 2)), 5),
+        (str(int('10001', 2)), 5),
+        (str(int('111110', 2)), 7),
+        (str(int('101111', 2)), 7),
+        (str(int('1101111', 2)), 9),
+        (str(int('10001000', 2)), 8),
+        (str(int('11001100', 2)), 10),
+        (str(int('10101010', 2)), 10),
+        (str(int('11011000', 2)), 10),
+        (str(int('10000000', 2)), 7),
+        ]
+
+for i, o in tests:
+    result = solution(i)
+    print (i, result == o, result, o)