08-27-周三_17-09-29

node_modules/graphlibrary/lib/alg/topsort.js

@@ -0,0 +1,35 @@
+const _ = require('../lodash')
+
+module.exports = topsort
+topsort.CycleException = CycleException
+
+function topsort (g) {
+  const visited = {}
+  const stack = {}
+  const results = []
+
+  function visit (node) {
+    if (_.has(stack, node)) {
+      throw new CycleException()
+    }
+
+    if (!_.has(visited, node)) {
+      stack[node] = true
+      visited[node] = true
+      _.each(g.predecessors(node), visit)
+      delete stack[node]
+      results.push(node)
+    }
+  }
+
+  _.each(g.sinks(), visit)
+
+  if (_.size(visited) !== g.nodeCount()) {
+    throw new CycleException()
+  }
+
+  return results
+}
+
+function CycleException () {}
+CycleException.prototype = new Error() // must be an instance of Error to pass testing