我想用Python 3.x解決動態規劃(DP)方法中的揹包問題。我的電訊局長指示我們前往this code領先。我試圖實現它,如下所示:動態規劃方法 - 揹包謎題
def take_input(infile):
f_open = open(infile, 'r')
lines = []
for line in f_open:
lines.append(line.strip())
f_open.close()
return lines
def create_list(jewel_lines):
#turns the jewels into a list of lists
jewels_list = []
for x in jewel_lines:
weight = x.split()[0]
value = x.split()[1]
jewels_list.append((int(value), int(weight)))
jewels_list = sorted(jewels_list, key = lambda x : (-x[0], x[1]))
return jewels_list
def dynamic_grab(items, max_weight):
table = [[0 for weight in range(max_weight+1)] for j in range(len(items)+1)]
for j in range(1,len(items)+1):
val= items[j-1][0]
wt= items[j-1][1]
for weight in range(1, max_weight+1):
if wt > weight:
table[j][weight] = table[j-1][weight]
else:
table[j][weight] = max(table[j-1][weight],table[j-1][weight-wt] + val)
result = []
weight = max_weight
for j in range(len(items),0,-1):
was_added = table[j][weight] != table[j-1][weight]
if was_added:
val = items[j-1][0]
wt = items[j-1][1]
result.append(items[j-1])
weight -= wt
return result
def totalvalue(comb):
#total of a combo of items
totwt = totval = 0
for val, wt in comb:
totwt += wt
totval += val
return (totval, -totwt) if totwt <= max_weight else (0,0)
#required setup of variables
infile = "JT_test1.txt"
given_input = take_input(infile)
max_weight = int(given_input[0])
given_input.pop(0)
jewels_list = create_list(given_input)
#test lines
print(jewels_list)
print(greedy_grab(jewels_list, max_weight))
bagged = dynamic_grab(jewels_list, max_weight)
print(totalvalue(bagged))
樣例如下。它是在格式線[0] = bag_max,線[1:]在形式(重量值):
575
125 3000
50 100
500 6000
25 30
我很困惑,該代碼的邏輯在它返回我元組,我不確定輸出元組代表什麼。我一直在看這一段時間,只是不明白代碼是指向我。任何幫助,將不勝感激。
創建列表函數是我寫的一個函數,所以我理解一個函數 - 創建一個重量,值對列表。總價值的元組我想要轉變爲實際的總價值,如果有意義的話 – idalsin