tunnelPaths.js

function tunnelPath(startPoint, endPoint, tunnels) {
    const manhattan = function(p1, p2) {
        return Math.abs(p1[0] - p2[0]) + Math.abs(p1[1] - p2[1]);
    }
    
    //init shortest to above ground between points
    let shortestPath = manhattan(startPoint, endPoint);
    
    const entrances = tunnels.map(item => [item[0], item[1]]);
    
    //find above ground distance between all entrances
    const distanceToEntrances = {
        'start':  entrances.map(p => manhattan(startPoint, p)),
        'end': entrances.map(p => manhattan(endPoint, p)),
    }
    
    for(let i = 0; i < entrances.length; i++) {
        //for all entrances track distance from start to entrance
            //for each other entrance add junctions + distance to end
        
        for(let j = 0; j < entrances.length; j++) {
            let currentPath = distanceToEntrances.start[i] + tunnels[i][2] + tunnels[j][2] + distanceToEntrances.end[j];
            if (currentPath < shortestPath) {
                shortestPath = currentPath;
            }
        }
    }
    
    return shortestPath;
    
}