C Array – Sorting Ascending and Descending in C Language
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Sorting Ascending and Descending in C – Program Description:
Write a C Program for Sorting Ascending and Descending in C programming language. We are going to use the qsort() function from the stdlib.h header file to sort the array.
We are going to write two programs in this article.
- Sorting Array in Ascending order using QSort.
- Sorting Array in Descending order using QSort.
Syntax of the QSort() function:
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void qsort (void* array, size_t num, size_t size, Â Â Â Â Â Â Â Â Â Â Â Â int (*compare_function)(const void*,const void*)); |
- array is the array to be sorted
- num is the size of the array
- size is the size of the data type. If you are using integer data, then it should sizeof(int)
- compare_function is a function pointer, which points to the comparison function.
1. Sorting Array in Ascending Order Using QSort Function:
Sort Array – Ascending Order Program Explanation:
- Declare the values array and desired variables.
- Prompt the user to provide the desired size and update size variable
- Create the read() and display() functions to read and print the array elements
- Take the array elements from the user and update the array using read() function.
- Display the array elements using the display() function.
- Now, We need to sort the array of elements using the qsort() function.
- The
qsort() function needs a
compare_function, Define a compare function named
compare_asc.
- Prototype of the compare_asc function is int compare_asc(const void *x, const void *y)
- Compare function compares the values pointed by the
x and
y variables and returns
- A Positive Number if the variable x should be placed after the variable y in ascending order
- A Negative value if variable x should be placed before y in ascending order
- or Returns Zero(0) if both the variables x and y are equal.
- Make the call to
qsort() function with parameters
values array,
size, and
sizeof(int), and
compare_asc function pointer.
- qsort(values, size, sizeof(int), compare_asc );
- Print the sorted Array on the console.
The QSort Compare function Logic for Sorting Array in Ascending Order:
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int compare_asc(const void *x, const void *y) { Â Â Â Â return (*(int*)x - *(int*)y); } |
Compare function compares the values pointed out by the x and y variables and returns
- A Positive Number if the variable x should be placed after the variable y in ascending order
- A Negative value if variable x should be placed before y in ascending order
- or Returns Zero(0) if both variables x and y are equal.
Sort Array in Ascending order using QSort function:
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/*     Program to sort the numbers using qsort inbuilt function     Author: SillyCodes.com */  #include <stdio.h> #include <stdlib.h>  int compare_asc(const void *x, const void *y) {     // Compare the values pointed to by 'x' and 'y' and return     // a negative value if 'x' should be placed before 'y' in ascending order,     // or a positive value if 'x' should be placed after 'y' in ascending order,     // or 0 if they are equal     return (*(int*)x - *(int*)y); }   /** * @brief  - Read the user input and update the 'values' array * * @param values - 'values' array * @param size    - size of the 'values' array */ void read(int values[], int size) {     int i;     // User input for array elements     printf("Please enter array elements(%d) : ", size);     for(i = 0; i < size; i++)     {         // printf("values[%d] : ", i);         scanf("%d", &values[i]);     } }  /** * @brief  - Display the 'values' array * * @param values - Array * @param size    - Array size */ void display(int values[], int size) {     int i;     for(i = 0; i < size; i++)     {         printf("%d ", values[i]);        }     printf("\n"); }  int main() {      // declare the 'values' array     int values[100];     int i, j, size, temp;      printf("Enter desired array size(1-100): ");     scanf("%d", &size);      // User input for array elements     read(values, size);         // Print the original array     printf("Original Array: ");     display(values, size);      // call 'qsort' with 'compare_asc' function     // 'compare_asc' is function pointer with     // int (*_PtFuncCompare)(const void *, const void *)) syntax     qsort(values, size, sizeof(int), compare_asc );      // Print the sorted array     printf("Sorted Array (Ascending Order): ");     display(values, size);      return 0; } |
Program Output:
Compile and Run the program using GCC (any compiler)
Test 1:
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$ gcc sort-array-qsort.c $ ./a.out Enter desired array size(1-100): 10 Please enter array elements(10) : 45 85 25 14 -52 -63 0 74 63 25 Original Array: 45 85 25 14 -52 -63 0 74 63 25 Sorted Array (Ascending Order): -63 -52 0 14 25 25 45 63 74 85 $ |
Test 2:
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$ ./a.out Enter desired array size(1-100): 8 Please enter array elements(8) : 88 77 66 55 44 33 22 11 Original Array: 88 77 66 55 44 33 22 11 Sorted Array (Ascending Order): 11 22 33 44 55 66 77 88 $ ./a.out Enter desired array size(1-100): 4 Please enter array elements(4) : 54-98 63 -5 Original Array: 54 -98 63 -5 Sorted Array (Ascending Order): -98 -5 54 63 $ |
The program is providing the expected output.
2. Sorting Array in Descending Order Using QSort Function:
Sort Array – Descending Order Program Explanation:
The program is very similar to the above Ascending order program except for the compare function ( compare_func).
We need to change the compare function so that, the qsort() function sorts the array in descending order.
Compare function logic for QSort() to sort elements in Descending order:
Define a compare function named compare_dsc.
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int compare_dsc(const void *x, const void *y) { Â Â return (*(int*)y - *(int*)x); } |
- Prototype of the compare_dsc function is int compare_dsc(const void *x, const void *y)
- Compare function compares the values pointed out by the
x and
y variables and returns
- A Positive value if variable x should be placed before y in descending order
- A Negative Number if the variable x should be placed after the variable y in descending order
- or Returns Zero(0) if both variables x and y are equal.
Sort Array in Descending order using QSort function:
Here is the program to sort the array in descending order using the qsort() function in the c programming language.
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/*     Program to sort the numbers using qsort inbuilt function     Author: SillyCodes.com */  #include <stdio.h> #include <stdlib.h>   int compare_dsc(const void *x, const void *y) {     // Compare the values pointed to by 'x' and 'y' and return     // a positive value if 'x' should be placed before 'y' in descending order,     // or a negative value if 'x' should be placed after 'y' in descending order,     // or 0 if they are equal     return (*(int*)y - *(int*)x); }   /** * @brief  - Read the user input and update the 'values' array * * @param values - 'values' array * @param size    - size of the 'values' array */ void read(int values[], int size) {     int i;     // User input for array elements     printf("Please enter array elements(%d) : ", size);     for(i = 0; i < size; i++)     {         // printf("values[%d] : ", i);         scanf("%d", &values[i]);     } }  /** * @brief  - Display the 'values' array * * @param values - Array * @param size    - Array size */ void display(int values[], int size) {     int i;     for(i = 0; i < size; i++)     {         printf("%d ", values[i]);        }     printf("\n"); }  int main() {      // declare the 'values' array     int values[100];     int i, j, size, temp;      printf("Enter desired array size(1-100): ");     scanf("%d", &size);      // User input for array elements     read(values, size);         // Print the original array     printf("Original Array: ");     display(values, size);      // call 'qsort' with 'compare_dsc' function     // 'compare_dsc' is function pointer with     // int (*_PtFuncCompare)(const void *, const void *)) syntax     qsort(values, size, sizeof(int), compare_dsc );      // Print the sorted array     printf("Sorted Array (Descending Order): ");     display(values, size);      return 0; } |
Program Output:
Compile and Run the Program.
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$ gcc sort-array-desc-qsort.c $ ./a.out Enter desired array size(1-100): 8 Please enter array elements(8) : 57 -5 -6 32 85 94 0 14 Original Array: 57 -5 -6 32 85 94 0 14 Sorted Array (Descending Order): 94 85 57 32 14 0 -5 -6 $ ./a.out Enter desired array size(1-100): 6 Please enter array elements(6) : 111 222 333 777 888 999 Original Array: 111 222 333 777 888 999 Sorted Array (Descending Order): 999 888 777 333 222 111 $ ./a.out Enter desired array size(1-100): 3 Please enter array elements(3) : 5 0 -4 Original Array: 5 0 -4 Sorted Array (Descending Order): 5 0 -4 $ |
As we can from the above output, The program is sorting the array elements in descending order.
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