added rest of the code

21/input

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+Hit Points: 109
+Damage: 8
+Armor: 2

21/part1.py

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+#!/usr/bin/python
+
+import re
+from math import ceil
+
+RE_STORE_HEADER = re.compile(r'^(.*):.*$')
+RE_STORE_ITEM = re.compile(r'^(.*)\s+(\d+)\s+(\d+)\s+(\d+)')
+RE_INPUT = re.compile(r'^(.*):\s+(\d+)$')
+
+
+def read_file(filename):
+    file = open(filename, 'r')
+    while True:
+        line = file.readline()
+        if not line:
+            break
+        yield line
+
+
+def simulate(me, boss):
+    myWinTurns = 0
+    bossWinTurns = 0
+
+    myWinTurns = int(ceil(boss['Hit Points'] / max(1, me['Damage'] - boss['Armor'])))
+    bossWinTurns = int(ceil(me['Hit Points'] / max(1, boss['Damage'] - me['Armor'])))
+    return(myWinTurns, bossWinTurns)
+
+
+def calculate_possible_combinations(minSum, maxSum, pos, usage):
+    if pos == len(usage):
+        if sum(usage) >= minSum and sum(usage) <= maxSum:
+            yield usage
+        return
+
+    for x in range(2):
+        usage[pos] = x
+        for c in calculate_possible_combinations(minSum, maxSum, pos+1, usage):
+            yield c
+    usage[pos] = 0
+
+
+def calculate_sum_product(item, usage, key):
+    sum = 0
+    for x in range(len(item)):
+        sum += item[x][key]*usage[x]
+    return sum
+
+
+def buy(store):
+    # 1 Weapon
+    # 0-1 Armor
+    # 0-2 Rings
+
+    weapons = [0 for x in range(len(store['Weapons']))]
+    armor = [0 for x in range(len(store['Armor']))]
+    rings = [0 for x in range(len(store['Rings']))]
+
+    for w in calculate_possible_combinations(1, 1, 0, weapons):
+        for a in calculate_possible_combinations(0, 1, 0, armor):
+            for r in calculate_possible_combinations(0, 2, 0, rings):
+                costS = calculate_sum_product(store['Weapons'], w, 'Cost')
+                costS += calculate_sum_product(store['Armor'], a, 'Cost')
+                costS += calculate_sum_product(store['Rings'], r, 'Cost')
+                armorS = calculate_sum_product(store['Weapons'], w, 'Armor')
+                armorS += calculate_sum_product(store['Armor'], a, 'Armor')
+                armorS += calculate_sum_product(store['Rings'], r, 'Armor')
+                damageS = calculate_sum_product(store['Weapons'], w, 'Damage')
+                damageS += calculate_sum_product(store['Armor'], a, 'Damage')
+                damageS += calculate_sum_product(store['Rings'], r, 'Damage')
+                yield (costS, damageS, armorS)
+
+
+def main():
+
+    boss = dict()
+    store = dict()
+    me = dict()
+
+    for line in read_file('input'):
+        match = re.match(RE_INPUT, line)
+        boss[match.group(1)] = int(match.group(2))
+
+    store_group = None
+    for line in read_file('store'):
+        match = re.match(RE_STORE_HEADER, line)
+        if match:
+            store_group = match.group(1)
+            store[store_group] = []
+            continue
+        match = re.match(RE_STORE_ITEM, line)
+        if match:
+            item = dict()
+            item['Name'] = match.group(1).strip()
+            item['Cost'] = int(match.group(2))
+            item['Damage'] = int(match.group(3))
+            item['Armor'] = int(match.group(4))
+            store[store_group].append(item)
+
+    me['Hit Points'] = 100
+    me['Damage'] = 0
+    me['Armor'] = 0
+
+    for (c, d, a) in buy(store):
+        me['Damage'] = d
+        me['Armor'] = a
+        (turnMe, trunBoss) = simulate(me, boss)
+        if turnMe <= trunBoss:
+            print c
+
+if __name__ == "__main__":
+    main()

21/part2.py

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+#!/usr/bin/python
+
+import re
+from math import ceil
+
+RE_STORE_HEADER = re.compile(r'^(.*):.*$')
+RE_STORE_ITEM = re.compile(r'^(.*)\s+(\d+)\s+(\d+)\s+(\d+)')
+RE_INPUT = re.compile(r'^(.*):\s+(\d+)$')
+
+
+def read_file(filename):
+    file = open(filename, 'r')
+    while True:
+        line = file.readline()
+        if not line:
+            break
+        yield line
+
+
+def simulate(me, boss):
+    myWinTurns = 0
+    bossWinTurns = 0
+
+    myWinTurns = int(ceil(boss['Hit Points'] / max(1, me['Damage'] - boss['Armor'])))
+    bossWinTurns = int(ceil(me['Hit Points'] / max(1, boss['Damage'] - me['Armor'])))
+    return(myWinTurns, bossWinTurns)
+
+
+def calculate_possible_combinations(minSum, maxSum, pos, usage):
+    if pos == len(usage):
+        if sum(usage) >= minSum and sum(usage) <= maxSum:
+            yield usage
+        return
+
+    for x in range(2):
+        usage[pos] = x
+        for c in calculate_possible_combinations(minSum, maxSum, pos+1, usage):
+            yield c
+    usage[pos] = 0
+
+
+def calculate_sum_product(item, usage, key):
+    sum = 0
+    for x in range(len(item)):
+        sum += item[x][key]*usage[x]
+    return sum
+
+
+def buy(store):
+    # 1 Weapon
+    # 0-1 Armor
+    # 0-2 Rings
+
+    numWeapons = len(store['Weapons'])
+    numArmor = len(store['Armor'])
+    numRings = len(store['Rings'])
+
+    weapons = [0 for x in range(numWeapons)]
+    armor = [0 for x in range(numArmor)]
+    rings = [0 for x in range(numRings)]
+
+    for w in calculate_possible_combinations(1, numWeapons, 0, weapons):
+        for a in calculate_possible_combinations(0, numArmor, 0, armor):
+            for r in calculate_possible_combinations(0, numRings, 0, rings):
+                costS = calculate_sum_product(store['Weapons'], w, 'Cost')
+                costS += calculate_sum_product(store['Armor'], a, 'Cost')
+                costS += calculate_sum_product(store['Rings'], r, 'Cost')
+                armorS = calculate_sum_product(store['Weapons'], w, 'Armor')
+                armorS += calculate_sum_product(store['Armor'], a, 'Armor')
+                armorS += calculate_sum_product(store['Rings'], r, 'Armor')
+                damageS = calculate_sum_product(store['Weapons'], w, 'Damage')
+                damageS += calculate_sum_product(store['Armor'], a, 'Damage')
+                damageS += calculate_sum_product(store['Rings'], r, 'Damage')
+                yield (costS, damageS, armorS)
+
+
+def main():
+
+    boss = dict()
+    store = dict()
+    me = dict()
+
+    for line in read_file('input'):
+        match = re.match(RE_INPUT, line)
+        boss[match.group(1)] = int(match.group(2))
+
+    store_group = None
+    for line in read_file('store'):
+        match = re.match(RE_STORE_HEADER, line)
+        if match:
+            store_group = match.group(1)
+            store[store_group] = []
+            continue
+        match = re.match(RE_STORE_ITEM, line)
+        if match:
+            item = dict()
+            item['Name'] = match.group(1).strip()
+            item['Cost'] = int(match.group(2))
+            item['Damage'] = int(match.group(3))
+            item['Armor'] = int(match.group(4))
+            store[store_group].append(item)
+
+    me['Hit Points'] = 100
+    me['Damage'] = 0
+    me['Armor'] = 0
+
+    for (c, d, a) in buy(store):
+        me['Damage'] = d
+        me['Armor'] = a
+        (turnMe, trunBoss) = simulate(me, boss)
+        if turnMe >= trunBoss:
+            print c
+
+if __name__ == "__main__":
+    main()

21/readme

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+## part1
+
+    python part1.py | sort -n | head -1
+
+## part2
+
+There must be at least one weapon
+
+    python part2.py | sort -nr | head -1

21/store

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+Weapons:    Cost  Damage  Armor
+Dagger        8     4       0
+Shortsword   10     5       0
+Warhammer    25     6       0
+Longsword    40     7       0
+Greataxe     74     8       0
+
+Armor:      Cost  Damage  Armor
+Leather      13     0       1
+Chainmail    31     0       2
+Splintmail   53     0       3
+Bandedmail   75     0       4
+Platemail   102     0       5
+
+Rings:      Cost  Damage  Armor
+Damage +1    25     1       0
+Damage +2    50     2       0
+Damage +3   100     3       0
+Defense +1   20     0       1
+Defense +2   40     0       2
+Defense +3   80     0       3