run formatter in quickselect

This commit is contained in:
NunoSempere 2023-11-29 21:46:44 +00:00
parent 03ca3e3b0c
commit dc3f7eed4d
2 changed files with 62 additions and 51 deletions

View File

@ -3,3 +3,9 @@ build:
run:
./quickselect
## Formatter
STYLE_BLUEPRINT=webkit
FORMATTER=clang-format -i -style=$(STYLE_BLUEPRINT)
format:
$(FORMATTER) quickselect.c

View File

@ -2,63 +2,68 @@
#include <stdio.h>
#include <stdlib.h>
void swp(int i, int j, double xs[]){
double tmp = xs[i];
xs[i] = xs[j];
xs[j] = tmp;
void swp(int i, int j, double xs[])
{
double tmp = xs[i];
xs[i] = xs[j];
xs[j] = tmp;
}
void array_print(double xs[], int n){
printf("[");
for(int i=0; i<n;i++){
printf("%f, ", xs[i]);
}
printf("]\n");
}
int partition(int low, int high, double xs[], int length){
// To understand this function:
// - see the note after gt variable definition
// - go to commit 578bfa27 and the scratchpad/ folder in it, which has printfs sprinkled throughout
int pivot = low + floor((high-low)/2);
double pivot_value = xs[pivot];
swp(pivot, high, xs);
int gt = low; /* This pointer will iterate until finding an element which is greater than the pivot. Then it will move elements that are smaller before it--more specifically, it will move elements to its position and then increment. As a result all elements between gt and i will be greater than the pivot. */
for(int i=low; i<high; i++){
if(xs[i] < pivot_value){
swp(gt, i, xs);
gt++;
void array_print(double xs[], int n)
{
printf("[");
for (int i = 0; i < n; i++) {
printf("%f, ", xs[i]);
}
}
swp(high, gt, xs);
return gt;
printf("]\n");
}
double quickselect(int k, double xs[], int length){
int low = 0;
int high = length - 1;
for (;;){
if(low == high){
return xs[low];
int partition(int low, int high, double xs[], int length)
{
// To understand this function:
// - see the note after gt variable definition
// - go to commit 578bfa27 and the scratchpad/ folder in it, which has printfs sprinkled throughout
int pivot = low + floor((high - low) / 2);
double pivot_value = xs[pivot];
swp(pivot, high, xs);
int gt = low; /* This pointer will iterate until finding an element which is greater than the pivot. Then it will move elements that are smaller before it--more specifically, it will move elements to its position and then increment. As a result all elements between gt and i will be greater than the pivot. */
for (int i = low; i < high; i++) {
if (xs[i] < pivot_value) {
swp(gt, i, xs);
gt++;
}
}
int pivot = partition(low, high, xs, length);
if(pivot == k){
return xs[pivot];
}else if(k < pivot){
high = pivot - 1;
} else {
low = pivot + 1;
}
}
swp(high, gt, xs);
return gt;
}
int main(){
double xs[] = {2.1, 1.0, 6.0, 4.0, 7.0, -1.0, 2.0, 10.0};
int length = 8;
int k = 2;
array_print(xs, 8);
double result = quickselect(k, xs, length);
printf("The item in pos #%d is: %f\n", k, result);
array_print(xs, 8);
return 0;
double quickselect(int k, double xs[], int length)
{
int low = 0;
int high = length - 1;
for (;;) {
if (low == high) {
return xs[low];
}
int pivot = partition(low, high, xs, length);
if (pivot == k) {
return xs[pivot];
} else if (k < pivot) {
high = pivot - 1;
} else {
low = pivot + 1;
}
}
}
int main()
{
double xs[] = { 2.1, 1.0, 6.0, 4.0, 7.0, -1.0, 2.0, 10.0 };
int length = 8;
int k = 2;
array_print(xs, 8);
double result = quickselect(k, xs, length);
printf("The item in pos #%d is: %f\n", k, result);
array_print(xs, 8);
return 0;
}