Add sort.binary_search (uses interpolation sort for ordered numeric types)

This commit is contained in:
gingerBill
2020-05-23 13:57:24 +01:00
parent 4671207c61
commit 7d11ee605c
2 changed files with 55 additions and 1 deletions

View File

@@ -286,3 +286,44 @@ compare_strings :: proc(a, b: string) -> int {
y := transmute(mem.Raw_String)b;
return mem.compare_byte_ptrs(x.data, y.data, min(x.len, y.len));
}
binary_search :: proc(array: $A/[]$T, key: T) -> (index: int, found: bool)
where intrinsics.type_is_ordered(T) #no_bounds_check {
n := len(array);
switch n {
case 0:
return -1, false;
case 1:
if array[0] == key {
return 0, true;
}
return -1, false;
}
lo, hi := 0, n-1;
for array[hi] != array[lo] && key >= array[lo] && key <= array[hi] {
when intrinsics.type_is_ordered_numeric(T) {
// NOTE(bill): This is technically interpolation search
m := lo + int((key - array[lo]) * T(hi - lo) / (array[hi] - array[lo]));
} else {
m := (lo + hi)/2;
}
switch {
case array[m] < key:
lo = m + 1;
case key < array[m]:
hi = m - 1;
case:
return m, true;
}
}
if key == array[lo] {
return lo, true;
}
return -1, false;
}

View File

@@ -7,6 +7,7 @@ import "core:thread"
import "core:time"
import "core:reflect"
import "core:runtime"
import "core:sort"
import "intrinsics"
@@ -1978,7 +1979,19 @@ pure_procedures :: proc() {
}
main :: proc() {
when true {
x := [?]f32{1, 1, 5, 6, 7, 8, 9, 10, 15, 15};
i, ok := sort.binary_search(x[:], 7);
fmt.println(x);
fmt.println(i, ok);
y := [?]string{"apple", "hello", "goodbye", "what?"};
sort.quick_sort(y[:]);
j, y_ok := sort.binary_search(y[:], "goodbye");
fmt.println(y);
fmt.println(j, y_ok);
when false {
the_basics();
control_flow();
named_proc_return_parameters();