C++ help with STL - sort() function

Question

Another small question about STL:

i have Dictionary:

map <string,vector <Wordy> > Dictionary;

using structure Wordy:

struct Wordy{ int count; string word;}

also this structure have overloaded operator<

bool operator< (Wordy& One, Wordy& Two){return One.count<Two.count;}

but this sort() function from algorithm doesn't work!

sort(Dictionary.find(s)->second.begin(),Dictionary.find(s)->second.end());

@Martin: The OP isn't sorting the map, she's sorting a particular element of the map. — Kerrek SB
– Kerrek SB, Commented Jul 4, 2011 at 23:43

Xeo · Accepted Answer · 2011-07-04 21:00:11Z

8

Your operator< should take its parameters by reference-to-const, I think that might be it:

bool operator< (const Wordy& One, const Wordy& Two){return One.count<Two.count;}
//              ^^^^^             ^^^^^

answered Jul 4, 2011 at 21:00

Xeo

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Comments

Community · Accepted Answer · 2017-05-23 12:04:24Z

0

check the post How to use std::sort with a vector of structures and compare function? . it explains how to use sort with a customized predicate function

CommunityBot

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answered Jul 4, 2011 at 20:58

NirMH

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I don't think that's it. That question deals with a sort function that wasn't returning bool.

Why should you need a custom predicate, if you can (and want) to implement operator<?

@zdan: do you mean the bool operator<(...) function?

@NirMH: Yes, I meant the sort "predicate" not the sort function.