Question

我正在制作一个（非常复杂且不优雅）的Python代码，通过暴力破解三色图形，在我的主要代码块中，我试图包含一个声明＆＃ 34;如果通过循环的最大次数超过（某个任意数字），则跳出第一个（while a in range(0,len(vertices))）循环＆＃34;。

a = 0
steps = 0   
while a in range(0,len(vertices)):
    for j in newdict:
        steps+=1      #count number of times it goes through the loop
        print(steps)
        if a>=len(vertices) or steps>=100000:
            break     #this is where my error is occurring

        i = vertices[a]
        if dict1[i[0]]==dict1[i[1]] and (list(dict1.values()))!=j:   #if the adjacent vertices are the same color and we have not cycled back to our original dict1,
            dict1[i[1]]=colors[dict1[i[1]]+1]   #change color of the second vertex
            a = 0    #after a vertex is changed colors, I don't want it to keep going: I want the code to stop and reexamine from the top with this new value
            newdict.append(list(dict1.values()))   #running list of all previous dictionaries (attempted colorings): if our dictionary ever cycles through to something it already was, try again
            check = all(dict1[i[0]] != dict1[i[1]] for i in vertices)  # check all adjacent vertices are different colors
            if not check:
                continue
            elif check:
                break  #at any point throughout the code, if the graph is colorable, break the loop and jump to end instead of continuing to color
        elif dict1[i[0]]==dict1[i[1]]:  #if we do eventally cycle back to our original dict1, now we'll try changing the first vertex color
            dict1[i[0]] = colors[dict1[i[0]] + 1]
            a = 0
            newdict.append(list(dict1.values()))
            check = all(dict1[i[0]] != dict1[i[1]] for i in vertices)  # check all adjacent vertices are different colors
            if not check:
                continue
            elif check:
                break  #at any point throughout the code, if the graph is colorable, break the loop and jump to end instead of continuing to color
        else:
            a+=1

然而，我发现即使经过了超过100000步（我可以看到，因为我打印了步数），循环不会中断并变成无限循环，并且数字步骤继续超过100000.我应该包括另一个循环，

while steps < 100000:

而不只是在我的第一个循环中添加另一个条件？我是在犯一个语法错误，还是我的代码更深入的问题？

（完整代码可用here。）

Answer 1

你有两个循环

break

所以当你for j in newdict:时，它会打破内部循环，break你需要为while循环{{1}}添加另一个条件

Answer 2

在while语句中添加另一个条件，然后在中断之前设置此条件。

max = False
while a in range(0,len(vertices)) and not max:
...
    for j in newdict:
        ...
        if a>=len(vertices) or steps>=100000:
            max = True
            break     #this is where my error is occurring

Python＆＃34;如果超过最大步数，则打破循环＆＃34;

2 个答案: