Inserting in map >

Question

Why is the following code not inserting elements in the map<int, set<int> > ?

(The size of all the sets after executing the following code is 0.)

I am creating an adjacency list in this map.

map<int, set<int> > m;
cin>>n;
while(n--)
{
    cin>>t;
    int i=0;
    while(t--)
    {
        scanf("%d",&x);
        set<int> s;
        m[x] = s;
        if(i != 0)
            m[prev].insert(x);
        prev = x;
    }
}

Why are you copying an empty set `s` into `m[x]` (possibly something that's already there). Also - why are you never initializing `prev`? — Leeor, Nov 19 '14 at 19:20
`i` is 0, `i` is never changed, and you only insert if `i` is not 0. You would have spotted this quite easily if you ran it through a debugger. — Biffen, Nov 19 '14 at 19:20

score 2 · Accepted Answer · answered Nov 19 '14 at 19:21

2

You aren't ever changing i so i == 0 when it does the check if(i != 0).

answered Nov 19 '14 at 19:21

Jimi

901
7
11

Sorry for troubling you guys...This was one hell of a mistake! xD – piXel_pRo Nov 19 '14 at 20:01
No worries, mate! We've all been there :) – Jimi Nov 19 '14 at 20:05

score 1 · Answer 2 · answered Nov 19 '14 at 19:21

1

Your variable 'i' is always 0.
And you are only inserting elements into the set if 'i' is != 0

answered Nov 19 '14 at 19:21

Inserting in map >

2 Answers2