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Topological sort: Difference between revisions
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</lang>
=={{header|Nim}}==
<lang Nim>import sequtils, strutils, sets, tables, sugar
type StringSet = HashSet[string]
proc topSort(data: var OrderedTable[string, StringSet]) =
## Topologically sort the data in place.
var ranks: Table[string, Natural] # Maps the keys to a rank.
# Remove self dependencies.
for key, values in data.mpairs:
values.excl key
# Add extra items (i.e items present in values but not in keys).
for values in toSeq(data.values):
for value in values:
if value notin data:
data[value] = initHashSet[string]()
# Find ranks.
var deps = data # Working copy of the table.
var rank = 0
while deps.len > 0:
# Find a key with an empty dependency set.
var keyToRemove: string
for key, values in deps.pairs:
if values.card == 0:
keyToRemove = key
break
if keyToRemove.len == 0:
# Not found: there is a cycle.
raise newException(ValueError, "Unorderable items found: " & toSeq(deps.keys).join(", "))
# Assign a rank to the key and remove it from keys and values.
ranks[keyToRemove] = rank
inc rank
deps.del keyToRemove
for k, v in deps.mpairs:
v.excl keyToRemove
# Sort the original data according to the ranks.
data.sort((x, y) => cmp(ranks[x[0]], ranks[y[0]]))
when isMainModule:
const Data = {"des_system_lib": ["std", "synopsys", "std_cell_lib",
"des_system_lib", "dw02", "dw01",
"ramlib", "ieee"].toHashSet,
"dw01": ["ieee", "dw01", "dware", "gtech"].toHashSet,
"dw02": ["ieee", "dw02", "dware"].toHashSet,
"dw03": ["std", "synopsys", "dware", "dw03",
"dw02", "dw01", "ieee", "gtech"].toHashSet,
"dw04": ["dw04", "ieee", "dw01", "dware", "gtech"].toHashSet,
"dw05": ["dw05", "ieee", "dware"].toHashSet,
"dw06": ["dw06", "ieee", "dware"].toHashSet,
"dw07": ["ieee", "dware"].toHashSet,
"dware": ["ieee", "dware"].toHashSet,
"gtech": ["ieee", "gtech"].toHashSet,
"ramlib": ["std", "ieee"].toHashSet,
"std_cell_lib": ["ieee", "std_cell_lib"].toHashSet,
"synopsys": initHashSet[string]()}.toOrderedTable
# Process the original data (without cycle).
echo "Data without cycle. Order after sorting:"
var data = Data
try:
data.topSort()
for key in data.keys: echo key
except ValueError:
echo getCurrentExceptionMsg()
# Process the modified data (with a cycle).
echo "\nData with a cycle:"
data = Data
data["dw01"].incl "dw04"
try:
data.topSort()
for key in data.keys: echo key
except ValueError:
echo getCurrentExceptionMsg()</lang>
=={{header|Object Pascal}}==
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