Debugging 调试一个简单的haskell函数以将颜色放置到节点；graphColor"；

因此，我在haskell有一个任务，我一直坚持我的逻辑，这就是给我的问题：

graphColor查找图形的所有可能着色 着色是将节点分配给颜色 这样，如果两个节点通过一个节点连接，则它们必须具有不同的颜色 边缘

graphColor采用以下参数

颜色列表

节点列表

边列表（即节点对）

部分着色（即节点和颜色对的列表）

边的示例列表

e1 :: [Edge]
e1 = [(1,3),(2,1),(2,5),(3,1),(3,2),(3,3),(3,4),(3,5),(5,6),(2,6)]

e2 :: [Edge]
e2 = [(1,2),(2,3),(3,4),(1,3),(2,4),(1,4)]

type Code = [(Char,Char)]

-- domain of our code

domain1 :: [Char]
domain1 = ['a'..'z']

-- associated range

range1 :: [Char]
range1 = ['q'..'z'] ++ ['a'..'p']

-- create a code out of our domain and range
code1 :: Code
code1 = zip domain1 range1

graphColor

返回图形的所有完整着色，如果有多个解决方案，则列表不需要包含所有着色，只要它至少包含一个

例1： 例2： 这是迄今为止我的代码，它只返回空列表，不管发生什么

graphColor :: [Color] -> [Node] -> [Edge] -> Coloring -> [Coloring]
-- Fill in your code here
graphColor colors nodes edges solution
  | length nodes == length solution = [solution]
  | otherwise = concat [graphColor colors nodes edges (newSol : solution) |
                             x <- nodes, y <- colors,
                             newSol <- [(x,y)],
                             notRepeat solution edges x y,
                             notElem newSol solution]
notRepeat :: Coloring -> [Edge] -> Node -> Color -> Bool
notRepeat solution edges x y 
  | x `elem` [z | (z,_) <- solution] = False
  |otherwise = helpHelper edges [z | (z,y) <- solution] x

helpHelper edges matchedNodes x
   = x `elem` [z | y <- matchedNodes, (z,y) <- edges] ++
     [z | y <- matchedNodes, (y,z) <- edges]

graphColor:：[Color]->[Node]->[Edge]->Coloring->[Coloring]
--在这里填写您的代码
graphColor节点边解决方案
|长度节点==长度解决方案=[解决方案]
|否则=concat[图形颜色节点边（newSol:解决方案）|
x颜色->布尔
不重复解决方案边x y
|x`elem`[z |（z，|）
> take 1 (graphColor "abc" [1..4] e2 [])
[]

graphColor :: [Color] -> [Node] -> [Edge] -> Coloring -> [Coloring]
-- Fill in your code here
graphColor colors nodes edges solution
  | length nodes == length solution = [solution]
  | otherwise = concat [graphColor colors nodes edges (newSol : solution) |
                             x <- nodes, y <- colors,
                             newSol <- [(x,y)],
                             notRepeat solution edges x y,
                             notElem newSol solution]
notRepeat :: Coloring -> [Edge] -> Node -> Color -> Bool
notRepeat solution edges x y 
  | x `elem` [z | (z,_) <- solution] = False
  |otherwise = helpHelper edges [z | (z,y) <- solution] x

helpHelper edges matchedNodes x
   = x `elem` [z | y <- matchedNodes, (z,y) <- edges] ++
     [z | y <- matchedNodes, (y,z) <- edges]