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# Structure Sorting (By Multiple Rules) in C++

• Difficulty Level : Easy
• Last Updated : 16 Feb, 2023

Prerequisite : Structures in C
Name and marks in different subjects (physics, chemistry and maths) are given for all students. The task is to compute total marks and ranks of all students. And finally display all students sorted by rank.

Rank of student is computed using below rules.

1. If total marks are different, then students with higher marks gets better rank.
2. If total marks are same, then students with higher marks in Maths gets better rank.
3. If total marks are same and marks in Maths are also same, then students with better marks in Physics gets better rank.
4. If total marks are same and marks in both Maths and Physics are also same, then students with better marks in Chemistry gets better rank.
5. If all marks (total, Maths, Physics and Chemistry) are same, then any student can be assigned better rank.
Recommended Practice

We use below structure to store details of students.

```struct Student
{
string name; // Given
int math;  // Marks in math (Given)
int phy;   // Marks in Physics (Given)
int che;   // Marks in Chemistry (Given)
int total; // Total marks (To be filled)
int rank;  // Rank of student (To be filled)
};  ```

We use std::sort() for Structure Sorting. In Structure sorting, all the respective properties possessed by the structure object are sorted on the basis of one (or more) property of the object.
In this example, marks of students in different subjects are provided by user. These marks in individual subjects are added to calculate the total marks of the student, which is then used to sort different students on the basis of their ranks (as explained above).

Implementation:

## CPP

 `// C++ program to demonstrate structure sorting in C++` `#include ` `using` `namespace` `std;`   `struct` `Student ` `{` `    ``string name; ``// Given` `    ``int` `math; ``// Marks in math (Given)` `    ``int` `phy; ``// Marks in Physics (Given)` `    ``int` `che; ``// Marks in Chemistry (Given)` `    ``int` `total; ``// Total marks (To be filled)` `    ``int` `rank; ``// Rank of student (To be filled)` `};`   `// Function for comparing two students according` `// to given rules` `bool` `compareTwoStudents(Student a, Student b)` `{` `    ``// If total marks are not same then` `    ``// returns true for higher total` `    ``if` `(a.total != b.total)` `        ``return` `a.total > b.total;`   `    ``// If marks in Maths are same then` `    ``// returns true for higher marks` `    ``if` `(a.math != b.math)` `        ``return` `a.math > b.math;`   `    ``if` `(a.phy != b.phy)` `        ``return` `a.phy > b.phy;`   `    ``return` `(a.che > b.che);` `}`   `// Fills total marks and ranks of all Students` `void` `computeRanks(Student a[], ``int` `n)` `{` `    ``// To calculate total marks for all Students` `    ``for` `(``int` `i = 0; i < n; i++)` `        ``a[i].total = a[i].math + a[i].phy + a[i].che;`   `    ``// Sort structure array using user defined` `    ``// function compareTwoStudents()` `    ``sort(a, a + 5, compareTwoStudents);`   `    ``// Assigning ranks after sorting` `    ``for` `(``int` `i = 0; i < n; i++)` `        ``a[i].rank = i + 1;` `}`   `// Driver code` `int` `main()` `{` `    ``int` `n = 5;`   `    ``// array of structure objects` `    ``Student a[n];`   `    ``// Details of Student 1` `    ``a.name = ``"Bryan"``;` `    ``a.math = 80;` `    ``a.phy = 95;` `    ``a.che = 85;`   `    ``// Details of Student 2` `    ``a.name = ``"Kevin"``;` `    ``a.math = 95;` `    ``a.phy = 85;` `    ``a.che = 99;`   `    ``// Details of Student 3` `    ``a.name = ``"Nicky"``;` `    ``a.math = 95;` `    ``a.phy = 85;` `    ``a.che = 80;`   `    ``// Details of Student 4` `    ``a.name = ``"Steve"``;` `    ``a.math = 80;` `    ``a.phy = 70;` `    ``a.che = 90;`   `    ``// Details of Student 5` `    ``a.name = ``"Rohan"``;` `    ``a.math = 80;` `    ``a.phy = 80;` `    ``a.che = 80;`   `    ``computeRanks(a, n);`   `    ``// Column names for displaying data` `    ``cout << ``"Rank"` `         ``<< ``" "` `         ``<< ``"Name"` `         ``<< ``"     "``;` `    ``cout << ``"Maths"` `         ``<< ``" "` `         ``<< ``"Physics"` `         ``<< ``" "` `         ``<< ``"Chemistry"``;` `    ``cout << ``" "` `         ``<< ``"Total\n"``;`   `    ``// Display details of Students` `    ``for` `(``int` `i = 0; i < n; i++) {` `        ``cout << a[i].rank << ``"    "``;` `        ``cout << a[i].name << ``"      "``;` `        ``cout << a[i].math << ``"     "` `<< a[i].phy << ``"     "` `             ``<< a[i].che << ``"       "``;` `        ``cout << a[i].total << ``" "``;` `        ``cout << ``"\n"``;` `    ``}`   `    ``return` `0;` `}`

Output

```Rank Name     Maths Physics Chemistry Total
1    Kevin      95     85     99       279
2    Nicky      95     85     80       260
3    Bryan      80     95     85       260
4    Rohan      80     80     80       240
5    Steve      80     70     90       240 ```

Time complexity : O(nlogn)

Auxiliary Space :O(n)

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