Can I use vector sort function in my own struct? always compiler error

Question

[Error] 'class std::vector' has no member named 'sort' which sort can use in struct and how to use? sorry for my bad english.

typedef struct name
{
    int x,y;
}name;

int main()
{
    int n,m,i;
    vector<name> a(10000);
    while(scanf("%d%d",&n,&m)!=EOF)
    {
        if(n==0&m==0)
        {
            break;
        }   
        a.clear();
        for(i=0;i<n;i++)
        {
            scanf("%d",&a[i].x);
            a[i].y=a[i].x%m;
        }
        a.sort();
        for(i=0;i<n;i++)
        {
            printf("%d\n",a[i].x);
        }
    }
    return 0;
}

Some general notes about your code: In C++ you don't need `typedef` for structures or classes; Don't set the size of the vector, add elements to it as needed; Don't use anonymous one-letter variable names, use descriptive names; Write comments to tell what the code does, and why it does it that way; Learn how to use the C++ input/output streams `cin` and `cout`; And lastly, there's no vector `sort` member function, but there is a [`std::sort`](https://en.cppreference.com/w/cpp/algorithm/sort) function which can sort any container. — Some programmer dude, Apr 27 '20 at 15:12
You'll also need a way to compare two `name` objects. How do you know if one `name` is less than another `name`? — JohnFilleau, Apr 27 '20 at 15:14
Oh and some extra notes: Split up the program into separate parts, preferably using functions;. For example one function to read input, then sort the vector (if it's really needed), then a function to do the processing, and lastly a function for the output.. Mixing input, algorithm and output makes the code harder to read, understand, maintain and debug. — Some programmer dude, Apr 27 '20 at 15:15
Your question looks like a duplicate of https://stackoverflow.com/questions/1380463/sorting-a-vector-of-custom-objects. Please search for existing questions before asking. — Xavier Lamorlette, Apr 27 '20 at 21:16

score 1 · Answer 1 · answered Apr 27 '20 at 15:16

1

vector doesn't have a sort function. Instead, use std::sort, and implement an operator< for your struct.

struct name
{
    int x,y;
    bool operator<( const name &other ) const {
        return x < other.x; // modify to whatever sorting conditions you need
    }
};

Then for calling sort, do

std::sort( a.begin(), a.end() );

answered Apr 27 '20 at 15:16

ChrisMM

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There is no need to alter the `struct`. The 3 argument version of `std::sort` is what would be used. – PaulMcKenzie Apr 27 '20 at 15:26
@PaulMcKenzie, depends on how often it'll be sorted. If it's sorted in more than one place, I prefer altering the struct. – ChrisMM Apr 27 '20 at 16:25
You could simply create a separate lambda function and use that. The point is that when you put an `operator – PaulMcKenzie Apr 28 '20 at 01:42

PaulMcKenzie · Answer 2 · 2020-04-28T01:46:55.800

Since std::vector has no sort() member function, you should use std::sort using the third argument as the sorting predicate. By doing so, you are not changing the internals of the struct you are sorting by adding an operator <:

#include <algorithm>
#include <vector>
struct name
{
    int x,y;
};

int main()
{
   std::vector<name> a(10000);

   // assuming you want to sort by x-coordinate  
   std::sort(a.begin(), a.end(), [](name& n1, name& n2) { return n1.x < n2.x; });
}

You can also create a separate lambda function:

#include <algorithm>
#include <vector>
struct name
{
    int x,y;
};

int main()
{
   std::vector<name> a(10000);
   auto comp = [](name& n1, name& n2) { return n1.x < n2.x; };

   // assuming you want to sort by x-coordinate  
   std::sort(a.begin(), a.end(), comp);
}

Can I use vector sort function in my own struct? always compiler error

2 Answers2