Hi, i found this piece of code in K&R book, but i have not understood how it works, page 74,

for example, what represent "int left, int right" variables and how should i use it?

I know this is not the complete qsort code inside standard library.

i tried to implement it :Code:/* qsort: sort v[left]...v[right] into increasing order */ void qsort(int v[], int left, int right) { int i, last; void swap(int v[], int i, int j); if (left >= right) /* do nothing if array contains */ return; /* fewer than two elements */ swap(v, left, (left + right)/2); /* move partition elem */ last = left; /* to v[0] */ for (i = left + 1; i <= right; i++) /* partition */ if (v[i] < v[left]) swap(v, ++last, i); swap(v, left, last); /* restore partition elem */ qsort(v, left, last-1); qsort(v, last+1, right); } /* swap: interchange v[i] and v[j] */ void swap(int v[], int i, int j) { int temp; temp = v[i]; v[i] = v[j]; v[j] = temp; }

I renamed qsort to quicksort, because it conflicts with the qsort in the standard library.

Code:#include <stdio.h> void qicksort( int v[], int left, int right ); int main(void) { int arr[] = { 3, 5, 1, 2, 4 }; qsort( arr, 0, 5 ); int i; for ( i = 0; i < 5; i++ ) printf("num=%d\n", arr[i] ); } /* qsort: sort v[left]...v[right] into increasing order */ void qicksort(int v[], int left, int right) { int i, last; void swap(int v[], int i, int j); if (left >= right) /* do nothing if array contains */ return; /* fewer than two elements */ swap(v, left, (left + right)/2); /* move partition elem */ last = left; /* to v[0] */ for (i = left + 1; i <= right; i++) /* partition */ if (v[i] < v[left]) swap(v, ++last, i); swap(v, left, last); /* restore partition elem */ qicksort(v, left, last-1); qicksort(v, last+1, right); } /* swap: interchange v[i] and v[j] */ void swap(int v[], int i, int j) { int temp; temp = v[i]; v[i] = v[j]; v[j] = temp; }