Arjun Suresh (talk | contribs) |
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[[Complexities_of_Basic_Sorting_Algorithms |Complexity and no. of swaps required]] | [[Complexities_of_Basic_Sorting_Algorithms |Complexity and no. of swaps required]] | ||
| − | + | <metadesc>Quick sort program in C</metadesc> | |
<syntaxhighlight lang="c" name="quicksort"> | <syntaxhighlight lang="c" name="quicksort"> | ||
| Line 16: | Line 16: | ||
int i, j, p; | int i, j, p; | ||
if(start >= end) | if(start >= end) | ||
| − | |||
return; | return; | ||
| − | + | ||
i = p = start, j = end; | i = p = start, j = end; | ||
while(i < j)// Finds the no. of elements in the array < a[p] from the beginning and swaps with the no. of elements in the array greater than a[p] from the end | while(i < j)// Finds the no. of elements in the array < a[p] from the beginning and swaps with the no. of elements in the array greater than a[p] from the end | ||
| Line 27: | Line 26: | ||
j--; | j--; | ||
if(i < j) | if(i < j) | ||
| − | |||
swap(&a[i], &a[j]); | swap(&a[i], &a[j]); | ||
| − | |||
} | } | ||
swap(&a[j], &a[p]); | swap(&a[j], &a[p]); | ||
| Line 40: | Line 37: | ||
int i; | int i; | ||
for(i = 0; i < n; i++) | for(i = 0; i < n; i++) | ||
| − | |||
printf("%d ",a[i]); | printf("%d ",a[i]); | ||
| − | |||
} | } | ||
| Line 71: | Line 66: | ||
[[Category: Arrays]] | [[Category: Arrays]] | ||
| + | [[Category:Sorting]] | ||
Complexity and no. of swaps required
<syntaxhighlight lang="c" name="quicksort">
void swap(int *a, int *b) { int temp = *a; *a = *b; *b = temp; }
void qsort(int a[], int start, int end) { int i, j, p; if(start >= end) return;
i = p = start, j = end; while(i < j)// Finds the no. of elements in the array < a[p] from the beginning and swaps with the no. of elements in the array greater than a[p] from the end { while(a[i] <= a[p] && i < end) i++; while(a[j] > a[p]) //( > ensures j never comes equal to p) j--; if(i < j) swap(&a[i], &a[j]); } swap(&a[j], &a[p]); qsort(a, start, j-1); qsort(a, j + 1, end); }
void printArray(int a[], int n) { int i; for(i = 0; i < n; i++) printf("%d ",a[i]); }
int main() { char str[20]; int num[100]; int i = 0; printf("Enter the numbers to sort (. to stop): "); while(1) { scanf("%s",str); if(str[0] == '.') break; sscanf(str, "%d", &num[i++]); } qsort(num, 0, i-1); printf("The sorted numbers are: "); printArray(num, i); printf("\n");
return 0;
} </syntaxhighlight>
Complexity and no. of swaps required
<syntaxhighlight lang="c" name="quicksort">
void swap(int *a, int *b) { int temp = *a; *a = *b; *b = temp; }
void qsort(int a[], int start, int end) { int i, j, p; if(start >= end) { return; } i = p = start, j = end; while(i < j)// Finds the no. of elements in the array < a[p] from the beginning and swaps with the no. of elements in the array greater than a[p] from the end { while(a[i] <= a[p] && i < end) i++; while(a[j] > a[p]) //( > ensures j never comes equal to p) j--; if(i < j) { swap(&a[i], &a[j]); } } swap(&a[j], &a[p]); qsort(a, start, j-1); qsort(a, j + 1, end); }
void printArray(int a[], int n) { int i; for(i = 0; i < n; i++) { printf("%d ",a[i]); } }
int main() { char str[20]; int num[100]; int i = 0; printf("Enter the numbers to sort (. to stop): "); while(1) { scanf("%s",str); if(str[0] == '.') break; sscanf(str, "%d", &num[i++]); } qsort(num, 0, i-1); printf("The sorted numbers are: "); printArray(num, i); printf("\n");
return 0;
} </syntaxhighlight>
GATECSE