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C program to sort an array in ascending order

  • Difficulty Level : Easy
  • Last Updated : 31 May, 2021

Given an array arr[] of size N, the task is to sort this array in ascending order in C.

Input: arr[] = {0, 23, 14, 12, 9}
Output: {0, 9, 12, 14, 23}

Input: arr[] = {7, 0, 2}
Output: {0, 2, 7}

There are many ways by which the array can be sorted in ascending order, like:  

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For simplicity, we will be using Selection Sort in this article.
The array can be sorted in ascending order by repeatedly finding the minimum element (considering ascending order) from unsorted part and putting it at the beginning. The algorithm maintains two subarrays in a given array. 

  1. The subarray which is already sorted.
  2. Remaining subarray which is unsorted.

In every iteration of selection sort, the minimum element (considering ascending order) from the unsorted subarray is picked and moved to the sorted subarray.
Below is the implementation of the above approach: 


// C program to sort the array in an
// ascending order using selection sort
#include <stdio.h>
void swap(int* xp, int* yp)
    int temp = *xp;
    *xp = *yp;
    *yp = temp;
// Function to perform Selection Sort
void selectionSort(int arr[], int n)
    int i, j, min_idx;
    // One by one move boundary of unsorted subarray
    for (i = 0; i < n - 1; i++) {
        // Find the minimum element in unsorted array
        min_idx = i;
        for (j = i + 1; j < n; j++)
            if (arr[j] < arr[min_idx])
                min_idx = j;
        // Swap the found minimum element
        // with the first element
        swap(&arr[min_idx], &arr[i]);
// Function to print an array
void printArray(int arr[], int size)
    int i;
    for (i = 0; i < size; i++)
        printf("%d ", arr[i]);
// Driver code
int main()
    int arr[] = { 0, 23, 14, 12, 9 };
    int n = sizeof(arr) / sizeof(arr[0]);
    printf("Original array: \n");
    printArray(arr, n);
    selectionSort(arr, n);
    printf("\nSorted array in Ascending order: \n");
    printArray(arr, n);
    return 0;
Original array: 
0 23 14 12 9 

Sorted array in Ascending order: 
0 9 12 14 23


Time Complexity: O(N2)

Auxiliary Space: O(1)

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