Adding to a vector of pair

Question

I have a vector of pair like such   vector lt pair lt string double gt  gt  revenue    I want to add a string and a double from a map like this   revenue i  first    string   revenue i  second   map i  second    But since revenue isn t initialized  it comes up with an out of bounds error  So I tried using vector  push back like this   revenue push back  string  map i  second     But that says cannot take two arguments  So how can I add to this vector of pair

User · Answer

Using emplace back function is way better than any other method since it creates an object in-place of type T where vector lt T gt   whereas push back expects an actual value from you   vector lt pair lt string double gt  gt  revenue      make pair function constructs a pair objects which is expected by push back revenue push back make pair  cash   12 32        emplace back passes the arguments to the constructor    function and gets the constructed object to the referenced space revenue emplace back  cash   12 32

User · Answer

Use std  make pair   revenue push back std  make pair  string  map i  second

User · Answer

revenue pushback  string  map i  second        But that says cannot take two arguments  So how can I add to this vector pair    You re on the right path  but think about it  what does your vector hold   It certainly doesn t hold a string and an int in one position  it holds a Pair   So      revenue push back  std  make pair   string   map i  second

User · Answer

Or you can use initialize list   revenue push back   string   map i  second

User · Answer

You can use std  make pair  revenue push back std  make pair  string  map i  second

User · Answer

Try using another temporary pair   pair lt string double gt  temp  vector lt pair lt string double gt  gt  revenue      Inside the loop temp first    string   temp second   map i  second  revenue push back temp

User · Answer

Read the following documentation   http   cplusplus com reference std utility make pair   or  http   en cppreference com w cpp utility pair make pair  I think that will help  Those sites are good resources for C    though the latter seems to be the preferred reference these days

User · Answer

IMHO  a very nice solution is to use c  11 emplace back function   revenue emplace back  string   map i  second     It just creates a new element in place

User · Answer

revenue push back pair lt string double gt    String  map i  second      this will work

User · Answer

As many people suggested  you could use std  make pair   But I would like to point out another method of doing the same   revenue push back   string  map i  second      push back   accepts a single parameter  so you could use      to achieve this

[c++] Adding to a vector of pair

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