Question

我目前正在学习有关算法的课程。我已经成功完成了这项作业。所有测试用例都通过了。我的代码看起来很乱，我想知道Python中是否有任何可用的东西可以帮助我更快地运行代码。谢谢

问题陈述如下：您将获得一个原始计算器，该计算器可以执行以下三个操作：当前数字：乘以2，乘以3，或加1。您的目标被赋予正整数，找到获得数量所需的最小操作数从数字1开始。

# Uses python3
import sys

def optimal_sequence(m):
    a=[0,0]
    for i in range(2,m+1):
        if i%3==0 and i%2==0:
            a.append(min(a[i//2],a[i//3],a[i-1])+1)
        elif i%3==0:
            a.append(min(a[i//3],a[i-1])+1)
        elif i%2==0:
            a.append(min(a[i//2],a[i-1])+1)
        else:
            a.append((a[i-1])+1)
    return backtrack(a,m)
def backtrack(a,m):
    result=[]
    result.append(m)
    current = m
    for i in range(a[-1],0,-1):
        if current%3==0 and a[current//3]==(i-1):
            current=current//3
            result.append(current)
        elif current%2==0 and a[current//2]==(i-1):
            current = current//2
            result.append(current)
        elif a[current-1]==(i-1):
            current = current-1
            result.append(current)
    return result

n = int(input())
if n == 1:
    print(0)
    print(1)
    sys.exit(0)

a= (optimal_sequence(n))
print(len(a)-1)
for x in reversed(a):
    print(x,end=" ")

Answer 1

我会从数字 n 开始对数字1进行广度优先搜索。跟踪已访问的号码，以便搜索回溯已访问的号码。对于访问的号码，请记住您是“到达”的号码，即到达 n 的最短路径中的下一个号码。

在我的测试中，该代码的运行速度比您的代码快：

from collections import deque

def findOperations(n):
    # Perform a BFS
    successor = {} # map number to next number in shortest path
    queue = deque() # queue with number pairs (curr, next)
    queue.append((n,None)) # start at n
    while True:
        curr, succ = queue.popleft()
        if not curr in successor: 
            successor[curr] = succ
            if curr == 1:
                break
            if curr%3 == 0: queue.append((curr//3, curr))
            if curr%2 == 0: queue.append((curr//2, curr))
            queue.append((curr-1, curr))
    # Create list from successor chain  
    result = []
    i = 1
    while i:
        result.append(i)
        i = successor[i]
    return result

使用参数 n 调用此函数：

findOperations(n)

它返回一个列表。

动态编程原始计算器代码优化

1 个答案: