确定在python中构建给定字符串的最低成本的程序
假设，我们必须构建一个长度为n的字符串'str'。要构建字符串，我们可以执行两个操作。
一个字符可以添加到str的末尾，成本为a。
可以将子字符串sub_str添加到成本r的str末尾。
我们必须计算构建字符串str的最低成本。
因此，如果输入类似于a=5,r=4,str='tpoint'，那么输出将是29。
要构建字符串'tpoint'，成本如下所述-
str = 't'; a new character added, therefore the cost is 5. str = 'tp'; a new character added, therefore the cost is 5. str = 'tpo'; a new character added, therefore the cost is 5. str = 'tpoi'; a new character added, therefore the cost is 5. str = 'tpoin'; a new character added, therefore the cost is 5. str = 'tpoint'; substring 't' is added, therefore the cost is 4.
总成本为5+5+5+5+5+4=29。
示例
让我们看看以下实现以获得更好的理解-
def solve(a, r, str):
size = len(str)
largest = []
low = 0
for upp in range(1, size+1):
while str[low:upp] not in str[:low]:
low += 1
largest.append(upp - low)
c = [a]
for i in range(1, size):
if largest[i] == 0:
c.append(c[-1] + a)
else:
c.append(min(c[-1] + a, c[i - largest[i]] + r))
return c[-1]
print(solve(5, 4, 'tpoint'))输入
5, 4, 'tpoint'输出结果
29