copy for the road

package.json

@@ -45,6 +45,6 @@
         "mocha-lcov-reporter": "^1.3.0"
     },
     "dependencies": {
-        "traversals": "^1.0.5"
+        "traversals": "^1.0.8"
     }
 }

src/lt.js

@@ -0,0 +1,148 @@
+/** ******************************************************************************************************************
+ * @file Describe what lt does.
+ * @author Julian Jensen <jjdanois@gmail.com>
+ * @since 1.0.0
+ * @date 12-Dec-2017
+ *********************************************************************************************************************/
+"use strict";
+
+const
+    { DFS } = require( 'traversals' );
+
+function lt( nodes )
+{
+    const
+        _link = w => w.ancestor = w.parent,
+        _compress = v => {
+            const u = v.ancestor;
+
+            if ( u === null ) return;
+
+            _compress( u );
+
+            if ( v.best.semi.pre > u.best.semi.pre )
+                v.best = u.best;
+
+            v.ancestor = u.ancestor;
+        },
+
+        _eval     = v => {
+            if ( v.ancestor === null ) return v;
+            _compress( v );
+            return v.best;
+        },
+
+        listOrder = nodes.map( ( succs, id ) => ( {
+            id,
+            pre:      -1,
+            succs,
+            preds:    [],
+            parent:   null,
+            semi:     null,
+            idom:     null,
+            ancestor: null,
+            best:     null,
+            bucket:   []
+        } ) ),
+        preOrder = [];
+
+    DFS( listOrder.map( n => n.succs ), {
+        edge: {
+            tree: ( from, to ) => listOrder[ to ].parent = listOrder[ from ]
+        },
+        pre: ( preNum, preIndex ) => {
+            const node = listOrder[ preNum ];
+
+            node.pre = preIndex;
+            node.semi = node;
+            node.best = node;
+
+            preOrder.push( node );
+        }
+    } );
+
+    listOrder.forEach( node => node.succs.forEach( s => listOrder[ s ].preds.push( node ) ) );
+
+    for ( let i = preOrder.length - 1; i > 0; --i )
+    {
+        const
+            w = preOrder[ i ],
+            p = w.parent;
+
+        if ( !p ) continue;
+
+        w.preds.forEach( v => {
+            const u = _eval( v );
+
+            if ( w.semi.pre > u.semi.pre )
+                w.semi = u.semi;
+        } );
+
+        w.semi.bucket.push( w );
+
+        _link( w );
+
+        p.bucket.forEach( v => {
+            const u = _eval( v );
+
+            v.idom = u.semi.pre < v.semi.pre ? u : p;
+        } );
+
+        p.bucket = [];
+    }
+
+    preOrder.forEach( w => {
+        if ( w.parent && w.idom.pre !== w.semi.pre )
+            w.idom = w.idom.idom;
+    } );
+
+    return listOrder.map( n => n.idom ? n.idom.pre : '-' );
+    // return listOrder;
+}
+
+const
+    testGraph = [
+        [ 1, 8 ],    // start
+        [ 2, 3 ],    // a
+        [ 3 ],       // b
+        [ 4, 5 ],    // c
+        [ 6 ],       // d
+        [ 6 ],       // e
+        [ 7, 2 ],    // f
+        [ 8 ],       // g
+        []           // end
+    ],
+    r = 0,
+    a = 1,
+    b = 2,
+    c = 3,
+    d = 4,
+    e = 5,
+    f = 6,
+    g = 7,
+    h = 8,
+    i = 9,
+    j = 10,
+    k = 11,
+    l = 12,
+
+    rlarger   = [
+        [ c, b, a ],    // r
+        [ d ],          // a
+        [ e, a, d ],    // b
+        [ f, g ],       // c
+        [ l ],          // d,
+        [ h ],          // e
+        [ i ],          // f
+        [ j, i ],       // g
+        [ e, k ],       // h
+        [ k ],          // i
+        [ i ],          // j
+        [ i, r ],       // k
+        [ h ]           // l
+    ],
+    result = lt( rlarger );
+    // result = lt( testGraph );
+
+console.log( result );
+