c++ - how to sort vector with multi data? -

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i have such vector:

struct statfaces {     std::string facename_1;     std::string facename_2;     float percentageperson ; };  std::vector<statfaces> listfaces_;

and want sort vector. want sort group. example.. 

i have facename_1 = john , facename_2 = kate , percentageperson = %90        facename_1 = john , facename_2 = nastia , percentageperson = %95        facename_1 = bill , facename_2 = jamie , percentageperson = %91         facename_1 = bill , facename_2 = anna , percentageperson = %72  output should ;   facename_1 = bill , facename_2 = jamie, percentageperson = %91 facename_1 = bill , facename_2 = anna , percentageperson = %72 facename_1 = john , facename_2 = nastia , percentageperson = %95 facename_1 = john , facename_2 = kate , percentageperson = %90

sort algorithm must group firstname_1 , sort according percentageperson

ps: not @ c++

you can pass custom comparison function std::sort. trivially implementable using std::tie:

#include <tuple> // std::tie  bool cmp(const statfaces& lhs, const statfaces& rhs) {   return std::tie(lhs.face_name1, lhs.percentageperson, lhs.facename_2) <          std::tie(rhs.face_name1, rhs.percentageperson, rhs.facename_2); }

then

#include <algorithm> // std::sort  std::sort(listfaces_.begin(), listfaces_.end(), cmp);

std::tie returns tuple of lvalue reference arguments, , there lexicographical less-than comparison bool operator< compares 2 of these tuples. effect perform less-than lexicographical comparison between 2 statfaces instances. used internally std::sort sort elements.

note: std::tie available in c++11 implementations. if don't have c++11 standard library implementation, can use std::tr1::tie header <tr1/tuple> or boost::tie. can implement comparison function cmp hand. exercise, both tedious , error prone.


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