Interview Question for Program Managers

Country: United States

Comment hidden because of low score. Click to expand.
of 1 vote

create the adjacency matrix from the given pairs, build all possible pairs (unidirectional) and add to result if no edge is present. In Java

public class RoadNetwork
    public static int[][] RoadBuilder(int nCities, int[][] builtRoads) {
        List<int[]> result = new ArrayList<>();
        boolean[][] adjMatrix = new boolean[nCities][nCities];
        for(int[] pair : builtRoads) {
            adjMatrix[pair[0]][pair[1]] = true;
            adjMatrix[pair[1]][pair[0]] = true;
        for(int u = 0; u < nCities; u++) {
            for(int v = u + 1; v < nCities; v++) {
                if(!adjMatrix[u][v]) {
                    result.add(new int[]{u, v});
        return result.toArray(new int[result.size()][2]);

    public static void main(String[] args) {
        int[][] test1 = new int[][]{{0, 1}, {1, 2}, {3, 2}};
                        RoadBuilder(4, test1))); // expected result should be {{0,2}, {0, 3}, {1, 3}}

- Chris May 23, 2017 | Flag Reply
Comment hidden because of low score. Click to expand.
of 1 vote

@sri The complexities are O(n^2). Temporally this can be explained as we can solve the problem by traversing the matrix, even if you can do it by traversing just half of it. Spatially is easy to see using the worst case in which there is no preexisting connection between the cities. In that case you would need to generate n-1 + n-2 ..... + 1 connections which has a quadratic cost. Basically the question is asking you to generate a clique, you can research the topic to get a deeper understanding.
Solution in Python:

def RoadBuilder(nCities, builtRoads):
    solutions = set()
    m = [ [0] * nCities for _ in xrange(nCities) ]
    for x,y in builtRoads:
        m[x][y] = 1
        m[y][x] = 1
    for x in xrange(nCities):
        for y in xrange(x+1, nCities):
            if m[x][y] == 0:
                solutions.add((x, y))
    return solutions

- Fernando May 24, 2017 | Flag Reply
Comment hidden because of low score. Click to expand.
of 0 vote

what are the time and space complexities?

- sri May 23, 2017 | Flag Reply
Comment hidden because of low score. Click to expand.
of 0 vote

#include <iostream>
using namespace std;
#include <vector>

vector<pair<int, int> > build_roads(int n, vector<pair<int, int> > in) {
    vector<vector<int> > matrix(n, vector<int>(n));
    for(vector<pair<int, int> >::iterator it = in.begin(); it != in.end(); ++it) {
        // check wheth the it->first and it->second within the limits
        matrix[it->first][it->second] = 1;
    vector<pair<int, int> > out;
    for(int i =0; i < n; i++) {
        for(int j=i+1; j<n; j++) {
            if (!matrix[i][j]) {
    return out;
int main() {
	// your code goes here
	int ara[][2] = {{0,1}, {1,2}, {2,3}};
	vector<pair<int, int> > in;
	for(int k = 0; k < sizeof(ara)/sizeof(ara[0]); k++) {
	    in.push_back(pair<int, int>(ara[k][0], ara[k][1]));
	vector<pair<int, int> > result = build_roads(4, in);
	for(vector<pair<int, int> >::iterator it = result.begin(); it != result.end(); ++it) {
	    cout << "{" << it->first<<"," <<it->second<<"}\n";
	return 0;

- ali.kheam May 29, 2017 | Flag Reply

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