C++ program: Sort array elements in descending order

Arranging data items in a proper form is an important task when solving some problems.

efficient way. The element sorting problem is one of the most commonly discussed Arrangement problem. In this article we will see how to arrange array elements Sort in descending order of their values ​​(in C).

There are many different sorting algorithms used in this field to sort numbers or non-numbers

elements in a given order. In this article, we will introduce only two simple methods sorting. The bubble sort and the selection sort. Let us see them one by one with proper Algorithm and C implementation code.

Sort the array in descending order using bubble sort technique

Bubble sorting technology is one of the most common and simple sorting methods.

elements in the array. This method checks two adjacent elements if they are correct order, then skip to the next elements, otherwise interchange them to place them in correct Arrange the other elements in order and then skip to the next element, otherwise swap them to place them in the correct position order. Then move towards right and do the same for the other pair of values. The bubble Arranged in order. Then move to the right and do the same with the other pair of values. bubble The sorting technique has several stages, at the end of each stage an element is placed in Correct expected position. Let’s take a look at the algorithm of bubble sort technique.

algorithm

• Read array A and its size n as input
• For the range of i from 0 to n-1, execute
  • For the range of j from 0 to n - 2, execute
  • If A[j]
  • Exchange A[j] and A[j 1]
• End if

end for

end for

Example

#include <iostream>
using namespace std;
void display( int arr[], int n ){
   for ( int i = 0; i < n; i++ ) {
      cout << arr[i] << ", ";
   }
}
void swap ( int &a, int &b ){
   int temp = a;
   a = b;
   b = temp;
}
void solve( int arr[], int n ){
   int i, j;
   for ( i = 0; i < n; i++ ) {
      for ( j = 0; j < n-1; j++ ) {
         if ( arr[j] < arr[ j+1 ] ) {
            swap( arr[j], arr[ j + 1 ] );
         }
      }
   }
}
int main(){
   int arr[] = {8, 45, 74, 12, 10, 36, 58, 96, 5, 2, 78, 44, 25, 12, 89, 95, 63, 84};
   int n = sizeof( arr ) / sizeof( arr[0] );
   cout << "Array before sorting: ";
   display(arr, n);
   solve( arr, n );
   cout << "\nArray After sorting: ";
   display(arr, n);
}

Output

Array before sorting: 8, 45, 74, 12, 10, 36, 58, 96, 5, 2, 78, 44, 25, 12, 89, 95, 63, 84, 
Array After sorting: 96, 95, 89, 84, 78, 74, 63, 58, 45, 44, 36, 25, 12, 12, 10, 8, 5, 2, 

Use selection sort technique to sort the array in descending order

In selection sort technique we find minimum element or maximum element Starting from index i in the given array, translated into Chinese: element from the given array starting from index i to the end of this array. Assume we are. Find the largest element. In each stage it finds the minimum value from index i to the end, then Place the element where it needs to be and search again for the next largest element the index i 1 and so on. After completing these phases, the entire array will be sorted index i 1 and so on. After completing these stages, the entire array will be sorted Correspondingly.

algorithm

• Read array A and its size n as input
• For the range of i from 0 to n-1, execute
  • ind := Index of the largest element of A from i to n
  • If A[ i ] < A[ ind ], then
    • Exchange A[ i ] and A[ ind ]
  • End if
• end for

Example

#include <iostream>
using namespace std;
void display( int arr[], int n ){
   for ( int i = 0; i < n; i++ ) {
      cout << arr[i] << ", ";
   }
}
void swap ( int &a, int &b ){
   int temp = a;
   a = b;
   b = temp;
}
int max_index( int arr[], int n, int s, int e ){
   int max = 0, max_ind = 0;
   for ( int i = s; i < e; i++ ) {
      if ( arr[i] > max ) {
         max = arr[i];
         max_ind = i;
      }
   }
   return max_ind;
}
void solve( int arr[], int n ){
   int i, j, ind;
   for ( i = 0; i < n; i++ ) {
      ind = max_index( arr, n, i, n );
      if ( arr[i] < arr[ ind ] ) {
         swap( arr[i], arr[ ind ] );
      }
   }
}
int main(){
   int arr[] = {8, 45, 74, 12, 10, 36, 58, 96, 5, 2, 78, 44, 25, 12,89, 95, 63, 84};
   int n = sizeof( arr ) / sizeof( arr[0] );
   cout << "Array before sorting: ";
   display(arr, n);
   solve( arr, n );
   cout << "\nArray After sorting: ";
   display(arr, n);
}

Output

Array before sorting: 8, 45, 74, 12, 10, 36, 58, 96, 5, 2, 78, 44, 25, 12, 89, 95, 63, 84, 
Array After sorting: 96, 95, 89, 84, 78, 74, 63, 58, 45, 44, 36, 25, 12, 12, 10, 8, 5, 2,

in conclusion

A sorting problem is a fundamental problem in which we arrange numbers or other values

in a given permutation logic. There are many different sorting techniques available here understand and implement Implemented and easy to understand. These two methods are bubble sorting technique and Selection sorting techniques. Using these two methods, we have sorted the dataset Descending (non-increasing) sort. These two sorting methods are not very efficient Respect the time, but they are easy to understand. Both methods require O(n2) time Amount of time, where n is the size of the input. Bubble sort can be made faster with simple way Check if there is no swapping in any phase, the next consecutive phase will not happen Change anything.

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