/* head ends here */ void quicksort(int ar_size, int * ar) { int i, j, t; int pivot = 0; if((ar_size == 0) || (ar_size == 1)) { return; } int a[1000], b[1000], s1 = 0, s2 = 0; for(i = 1; < ar_size; i++) { if(ar[i] <= ar[pivot]) { a[s1++] = ar[i]; } else { b[s2++] = ar[i]; } } quicksort(s1, a); quicksort(s2, b); t = ar[pivot]; for(i = 0; < s1; i++) { ar[i] = a[i]; } ar[i] = t; for(i = 0; < s2; i++) { ar[s1 + +1] = b[i]; } for(i = 0; i< ar_size; i++) { printf("%d ", ar[i]); } printf("\n"); } /* tail starts here */ int main() { int _ar_size; scanf("%d", &_ar_size); int _ar[_ar_size], _ar_i; for(_ar_i = 0; _ar_i < _ar_size; _ar_i++) { scanf("%d", &_ar[_ar_i]); } quicksort(_ar_size, _ar); return 0; }
if understand correctly want understand how quicksort works. suggest take @ this video.
now recursion. idea simple. have function specific in process calls itself. fine example factorial of number.
int factorial(int x) { if(x = 0) return 1; return x * factorial(x - 1); } so if call factorial(4); factorial(4)= 4 * factorial(3)= 4 * 3 * factorial(2) = 4 * 3 * 2 * factorial(1) = 4 * 3 * 2 * 1 * factorial(0) = 4 * 3 * 2 * 1 * 1 = 24
