v1.js

/**
 * Auto-generated code below aims at helping you parse
 * the standard input according to the problem statement.
 **/

var inputs = readline().split(' ');
var N = parseInt(inputs[0]); // the total number of nodes in the level, including the gateways
var L = parseInt(inputs[1]); // the number of links
var E = parseInt(inputs[2]); // the number of exit 

var links       = []
var gates       = []
var brokenLinks = []

for (var i = 0; i < L; i++) {
    links[i] = [0,0];   
}

for (var i = 0; i < L; i++) {
    var inputs = readline().split(' ');
    var N1 = parseInt(inputs[0]); // N1 and N2 defines a link between these nodes
    var N2 = parseInt(inputs[1]);
    
    links[N1][N2] = 1;
}

for (var i = 0; i < E; i++) {
    var EI = parseInt(readline()); // the index of a gateway node
    gates.push(EI);    
}

// game loop
while (true) {
    var SI = parseInt(readline()); // The index of the node on which the Skynet agent is positioned this turn

    // Write an action using print()
    // To debug: printErr('Debug messages...');
    gates.forEach((g) => {
        if (links[SI][g] == 1 || links[g][SI] == 1) {
            print( ((SI < g) ? [SI, g] : [g, SI]).join(" "));
        }
    });

    //print('0 1'); // Example: 0 1 are the indices of the nodes you wish to sever the link between
}

v2.js

/**
 * Auto-generated code below aims at helping you parse
 * the standard input according to the problem statement.
 **/

/**
 * Check if there are any successor node (n), from the given list, 
 * that has a relation with one of gateway nodes.
 * 
 * It prints indices of the nodes you wish to delete in order to isolate block the agent.
 * 
 * @param {Array[int]} list of node indices
 */
let checkSuccessors = (successors) => {
    if (!successors.length) {
         return  
    } else {
        let n = successors.shift();
        
        gates.forEach((g) => {
            if (links[n][g] == 1 || links[g][n] == 1) {
                print( ((n < g) ? [n, g] : [g, n]).join(" "));
            }
        });  
        
        // Also start the check recursively on successors of the node and the rest of successors.
        checkSuccessors(getSuccessorsOf(n));
        checkSuccessors(successors);
    }
}

/**
 * Return the list of successors of a given node indice.
 * 
 * @param {int} node indice.
 * @return {Array[int]} list of successor's indices.
 */
let getSuccessorsOf = (n) => {
    var s = $successors[n];
    printErr("$s["+n+"]="+s);
    return s;
}

var inputs = readline().split(' ');
var N = parseInt(inputs[0]); // the total number of nodes in the level, including the gateways
var L = parseInt(inputs[1]); // the number of links
var E = parseInt(inputs[2]); // the number of exit 


var links       = []; // The matrix that keep info about relations between nodes.
var gates       = []; // The list of gateway indices.
var brokenLinks = []; // The list of link that need to be brocken to isolate the agent.
var $successors = []; // The associative array that keeps successors of every nodes.

for (var i = 0; i < L; i++) {
    // Initializing links (zero filled matrix) and successors
    links[i] = [0,0];   
    $successors[i] = [];
}

for (var i = 0; i < L; i++) {
    var inputs = readline().split(' ');
    var N1 = parseInt(inputs[0]); // N1 and N2 defines a link between these nodes
    var N2 = parseInt(inputs[1]);
    
    // Assign 1 to the element in the matrix at position (i,i) = (N1,N2)
    links[N1][N2] = 1;
    
    // printErr("(i="+i+", N1="+N1+", N2="+N2+")");
    // Store sucessors of every nodes for later uses.
    $successors[N1].push(N2);   
    //printErr("$s["+N1+"]="+$successors[N1]);
}



for (var i = 0; i < E; i++) {
    var EI = parseInt(readline()); // the indices of a gateway node
    gates.push(EI);    
}

// game loop
while (true) {
    var SI = parseInt(readline()); // The indices of the node on which the Skynet agent is positioned this turn
    printErr(SI);
    
    // Start checking the indices of the agent and its successors.
    checkSuccessors([SI]);
}