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Commit 2c68424

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cd155

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add more version to 8.2, find one path

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Lines changed: 22 additions & 1 deletion

Original file line number	Diff line number	Diff line change
`@@ -104,7 +104,11 @@ permutateSeq existSeq (x:xs) = map (++ [x]) existSeq ++`
`104`	`104`
`105`	`105`	`Theoretically, it has 2^(c+r) different paths`
`106`	`106`
`107`		`- test case: allPaths (0,0) (2,2) [(1,1), (1,2)]`
	`107`	`+ 1. find all valid paths`
	`108`	`+ test case: allPaths (0,0) (2,2) [(1,1), (1,2)]`
	`109`	`+`
	`110`	`+ 2. find only one valid path`
	`111`	`+ test case: findOnePath (0,0) (3,3) [(1,1), (2,1), (3,1),(1,2),(1,3)]`
`108`	`112`	`-}`
`109`	`113`
`110`	`114`	`{-`
`@@ -167,3 +171,20 @@ removeNothing :: [Maybe(Nat, Nat)] -> [Maybe(Nat, Nat)]`
`167`	`171`	`removeNothing xs`
`168`	`172`	`\| xs!!(length xs -1) == Nothing = removeNothing $ init xs`
`169`	`173`	`\| otherwise = xs`
	`174`	`+`
	`175`	`+-- 8.2, find only one valid path`
	`176`	`+isValidPath :: (Nat, Nat) -> (Nat, Nat) -> [(Nat, Nat)] -> Bool`
	`177`	`+isValidPath (x, y) (c, r) constrs`
	`178`	`+ \| x == c && y == r = True`
	`179`	`+ \| x > c \|\| y > r = False`
	`180`	+ \| (x, y) `elem` constrs = False
	`181`	`+ \| otherwise = isValidPath (x+1, y) (c, r) constrs \|\|`
	`182`	`+ isValidPath (x, y+1) (c, r) constrs`
	`183`	`+`
	`184`	`+findOnePath :: (Nat, Nat) -> (Nat, Nat) -> [(Nat, Nat)] -> [(Nat, Nat)]`
	`185`	`+findOnePath (x, y) (c, r) constrs`
	`186`	`+ \| isValidPath (x+1, y) (c, r) constrs =`
	`187`	`+ (x+1, y): findOnePath(x+1, y) (c,r) constrs`
	`188`	`+ \| isValidPath (x, y+1) (c, r) constrs =`
	`189`	`+ (x, y+1): findOnePath(x, y+1) (c,r) constrs`
	`190`	`+ \| otherwise = []`

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