Question https://www.hackerrank.com/contests/w38/challenges/a-time-saving-affair

Solution https://www.hackerrank.com/contests/w38/challenges/a-time-saving-affair/submissions/code/1308726348

Please let me know what is wrong in this code.

Question https://www.hackerrank.com/contests/w38/challenges/a-time-saving-affair

Solution https://www.hackerrank.com/contests/w38/challenges/a-time-saving-affair/submissions/code/1308726348

Please let me know what is wrong in this code.

Your Implementation of was absolutely correct but the reason for some failing cases was the following block of code:

```
node x = nodes[nn.dest].get(i);
if(dist[nn.dest]+x.dist< dist[x.dest] )
{
dist[x.dest] = dist[nn.dest]+x.dist;
if((dist[nn.dest])/k%2==1){
long r = (dist[nn.dest]%k);
dist[x.dest] += k-r;
}
node xx = new node();
xx.dest=x.dest;
xx.dist=dist[x.dest];
queue.add(xx);
}
```

You are adding the extra waiting time only after you have considered that the current path is shorter than the path , What I mean to say is that you are not adding the extra waiting time before putting elements in your queue.

Let us consider an example , suppose you reach a node at time t = 4 and the weight of the edge that you will be traversing is just 1 unit. Now suppose that the traffic light is red at t = 4 when you reached the node , but since you do not consider the extra waiting time during the `if(dist[nn.dest]+x.dist< dist[x.dest] )`

statement , your code fails on some cases

I modified your code , check it.

I just did the following modification to your code:

```
long tempp = 0;
if((dist[nn.dest])/k%2==1){
long r = (dist[nn.dest]%k);
tempp += k-r;
}
if(dist[nn.dest]+x.dist + tempp < dist[x.dest] )
{
dist[x.dest] = dist[nn.dest]+x.dist + tempp;
node xx = new node();
xx.dest=x.dest;
xx.dist=dist[x.dest];
queue.add(xx);
}
}
```

Since we now consider the extra waiting time in the variable tempp , It passes all the cases where it failed.

I hope I was Able to help you , you can check a neat implementation of this question in c++ here.

Thank You !

4 Likes

I got it thnx