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import * as is from '../../is';
import Heap from '../../heap';
import { defaults } from '../../util';
const dijkstraDefaults = defaults({
root: null,
weight: edge => 1,
directed: false
});
let elesfn = ({
dijkstra: function( options ){
if( !is.plainObject(options) ){
let args = arguments;
options = { root: args[0], weight: args[1], directed: args[2] };
}
let { root, weight, directed } = dijkstraDefaults(options);
let eles = this;
let weightFn = weight;
let source = is.string( root ) ? this.filter( root )[0] : root[0];
let dist = {};
let prev = {};
let knownDist = {};
let { nodes, edges } = this.byGroup();
edges.unmergeBy( ele => ele.isLoop() );
let getDist = node => dist[ node.id() ];
let setDist = ( node, d ) => {
dist[ node.id() ] = d;
Q.updateItem( node );
};
let Q = new Heap( (a, b) => getDist(a) - getDist(b) );
for( let i = 0; i < nodes.length; i++ ){
let node = nodes[ i ];
dist[ node.id() ] = node.same( source ) ? 0 : Infinity;
Q.push( node );
}
let distBetween = ( u, v ) => {
let uvs = ( directed ? u.edgesTo(v) : u.edgesWith(v) ).intersect( edges );
let smallestDistance = Infinity;
let smallestEdge;
for( let i = 0; i < uvs.length; i++ ){
let edge = uvs[ i ];
let weight = weightFn( edge );
if( weight < smallestDistance || !smallestEdge ){
smallestDistance = weight;
smallestEdge = edge;
}
}
return {
edge: smallestEdge,
dist: smallestDistance
};
};
while( Q.size() > 0 ){
let u = Q.pop();
let smalletsDist = getDist( u );
let uid = u.id();
knownDist[ uid ] = smalletsDist;
if( smalletsDist === Infinity ){
continue;
}
let neighbors = u.neighborhood().intersect( nodes );
for( let i = 0; i < neighbors.length; i++ ){
let v = neighbors[ i ];
let vid = v.id();
let vDist = distBetween( u, v );
let alt = smalletsDist + vDist.dist;
if( alt < getDist( v ) ){
setDist( v, alt );
prev[ vid ] = {
node: u,
edge: vDist.edge
};
}
} // for
} // while
return {
distanceTo: function( node ){
let target = is.string( node ) ? nodes.filter( node )[0] : node[0];
return knownDist[ target.id() ];
},
pathTo: function( node ){
let target = is.string( node ) ? nodes.filter( node )[0] : node[0];
let S = [];
let u = target;
let uid = u.id();
if( target.length > 0 ){
S.unshift( target );
while( prev[ uid ] ){
let p = prev[ uid ];
S.unshift( p.edge );
S.unshift( p.node );
u = p.node;
uid = u.id();
}
}
return eles.spawn( S );
}
};
}
});
export default elesfn;
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