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Sorting a structure in C++

C++ - Sorting a Structure: Here, we are going to learn how to sort a structure in C++ programming language?
Submitted by Himanshu Singh Bisht, on November 09, 2018

Generally sorting is done on an array of integer or string but there may be a situation where sorting is based on the number but actual data may be some other value.

Example:

Suppose we have to sort names of student according to roll number. So a structure can be created which can be used to store roll number and names.

Declaration of structure:

    typedef struct value{
	    int roll;
	    string name;
    }data;

C++ Code to sort structure:

#include <bits/stdc++.h>
using namespace std;

typedef struct value{
	int roll;
	string name;
}data;

bool compare(data a, data b)
{
	//for descending order replace with a.roll >b.roll
	if(a.roll < b.roll)		
		return 1;
	else
		return 0;
}

int main()
{
	int n,i;

	cout<<"Enter the number of students\n";
	cin>>n;	

	data  array[n];//array of structure is created

	cout<<"Enter roll number and then name\n";
	for(i=0;i<n;i++)
	{
		cin>>array[i].roll;
		cin>>array[i].name;
	}

	sort(array,array+n,compare);

	cout<<"Sorted list..."<<endl;
	for(i=0;i<n;i++)
	{
		cout<<array[i].roll<<" ";
		cout<<array[i].name<<endl;
	}

	return 0;
}

Output

Enter the number of students
3
Enter roll number and then name
101 Amit
102 Abhishek
103 Shubham
Sorted list...
101 Amit
102 Abhishek
103 Shubham