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Fix bug and format code in QuickSort.c

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Libin Yang 2019-05-05 15:23:58 +08:00 committed by GitHub
parent 2fde23c6ed
commit 67e2e98311
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1 changed files with 60 additions and 58 deletions
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118
sorting/QuickSort.c
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@ -1,100 +1,102 @@
#include <stdio.h>
#include <stdlib.h>
/*Displays the array, passed to this method*/
void display(int arr[], int n)
{
void display(int arr[], int n){
int i;
for(i = 0; i < n; i++){
printf("%d ", arr[i]);
}
printf("\n");
int i;
for (i = 0; i < n; i++)
{
printf("%d ", arr[i]);
}
printf("\n");
}
/*Swap function to swap two values*/
void swap(int *first, int *second){
void swap(int *first, int *second)
{
int temp = *first;
*first = *second;
*second = temp;
int temp = *first;
*first = *second;
*second = temp;
}
/*Partition method which selects a pivot
and places each element which is less than the pivot value to its left
and the elements greater than the pivot value to its right
arr[] --- array to be partitioned
lower --- lower index
upper --- upper index
*/
int partition(int arr[], int lower, int upper){
int partition(int arr[], int lower, int upper)
{
int i = (lower - 1);
int i = (lower - 1);
int pivot = arr[upper]; // Selects last element as the pivot value
int pivot = arr[upper]; // Selects last element as the pivot value
int j ;
for(j = lower; j < upper ; j++){
int j;
for (j = lower; j < upper; j++)
{
if(arr[j] <= pivot){ // if current element is smaller than the pivot
if (arr[j] <= pivot)
{ // if current element is smaller than the pivot
i++; // increment the index of smaller element
swap(&arr[i], &arr[j]);
}
}
i++; // increment the index of smaller element
swap(&arr[i], &arr[j]);
}
}
swap(&arr[i + 1] , &arr[upper]); // places the last element i.e, the pivot to its correct position
return (i + 1);
swap(&arr[i + 1], &arr[upper]); // places the last element i.e, the pivot to its correct position
return (i + 1);
}
/*This is where the sorting of the array takes place
arr[] --- Array to be sorted
lower --- Starting index
upper --- Ending index
*/
void quickSort(int arr[], int lower, int upper){
void quickSort(int arr[], int lower, int upper)
{
if(upper > lower){
if (upper > lower)
{
// partitioning index is returned by the partition method , partition element is at its correct poition
// partitioning index is returned by the partition method , partition element is at its correct poition
int partitionIndex = partition(arr, lower, upper);
int partitionIndex = partition(arr, lower, upper);
// Sorting elements before and after the partition index
quickSort(arr, lower, partitionIndex - 1);
quickSort(arr, partitionIndex + 1, upper);
}
// Sorting elements before and after the partition index
quickSort(arr, lower, partitionIndex - 1);
quickSort(arr, partitionIndex + 1, upper);
}
}
int main()
{
int main(){
int n;
printf("Enter size of array:\n");
scanf("%d", &n); // E.g. 8
printf("Enter the elements of the array\n");
int i;
int *arr = (int *)malloc(sizeof(int) * n);
for (i = 0; i < n; i++)
{
scanf("%d", &arr[i]);
}
int n;
printf("Enter size of array:\n");
scanf("%d", &n); // E.g. 8
printf("Original array: ");
display(arr, n); // Original array : 10 11 9 8 4 7 3 8
printf("Enter the elements of the array\n");
int i;
int arr[n];
for(i = 0; i < n; i++){
scanf("%d", &arr[i] );
}
quickSort(arr, 0, n - 1);
printf("Original array: ");
display(arr, n); // Original array : 10 11 9 8 4 7 3 8
quickSort(arr, 0, n-1);
printf("Sorted array: ");
display(arr, n); // Sorted array : 3 4 7 8 8 9 10 11
return 0;
}
printf("Sorted array: ");
display(arr, n); // Sorted array : 3 4 7 8 8 9 10 11
getchar();
return 0;
}