topological sort

js/src/directed/predecessors.js

@@ -0,0 +1,9 @@
+
+const predecessors = function ( G , pred ) {
+
+	for ( let u of G.vertices( ) ) pred[u] = 0 ;
+	for ( let [ _ , v ] of G.edges( ) ) ++pred[v] ;
+
+} ;
+
+exports.predecessors = predecessors ;

js/src/directed/topologicalsort.js

@@ -0,0 +1,30 @@
+
+const topologicalsort = function* ( G , pred , queue ) {
+
+	predecessors( G , pred ) ;
+
+	for ( let u of G.vertices( ) ) {
+
+		if ( pred[u] === 0 ) queue.push( u ) ;
+
+	}
+
+	while ( !queue.empty( ) ) {
+
+		let u = queue.pop( ) ;
+
+		yield u ;
+
+		for ( let v of G.neighbours( u ) ) {
+
+			--pred[v] ;
+
+			if ( pred[v] === 0 ) queue.push( v ) ;
+
+		}
+
+	}
+
+} ;
+
+exports.topologicalsort = topologicalsort ;