CODEWITHSUNDEEP
c++stliterator
Naman
Naman

Reputation: 179

Difference between the rbegin and the end function in standard library

I have an implementation of a map where the ID is being stored as value and marks as key. This enables me to take advantage of the auto sorting in maps and lets me identify the ID of the element with highest marks.

for(map<int, int>::iterator i = marks.begin(); i != marks.end(); ++i)
    cout << i->first << "\t" << i->second << endl;
cout << marks.rbegin()->second << endl;
cout << marks.end()->second << endl;

produces this output:

312 3
420 4
512 2
752 1
1
420

The input sequence was the increasing order of values. Why does end() not display "1" but instead displays the key of the last pair inputted? What's the difference between rbegin() and end()?

Upvotes: 6

Views: 3375

Answers (1)

Cory Kramer
Cory Kramer

Reputation: 117971

rbegin is actually the last element of your container. end is one past the end of the container.

So marks.end()->second is undefined behavior.

Upvotes: 17

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