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Optimize binary search algorithm

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Benjamin Feng 2019-11-18 20:35:03 -06:00 committed by Andrew Kelley
parent 76f21852f6
commit aca1367533
1 changed files with 20 additions and 24 deletions
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44
lib/std/sort.zig
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@ -868,39 +868,35 @@ fn findLastBackward(comptime T: type, items: []T, value: T, range: Range, lessTh
}
fn binaryFirst(comptime T: type, items: []T, value: T, range: Range, lessThan: fn (T, T) bool) usize {
var start = range.start;
var end = range.end - 1;
var curr = range.start;
var size = range.length();
if (range.start >= range.end) return range.end;
while (start < end) {
const mid = start + (end - start) / 2;
if (lessThan(items[mid], value)) {
start = mid + 1;
} else {
end = mid;
while (size > 0) {
const offset = size % 2;
size /= 2;
const mid = items[curr + size];
if (lessThan(mid, value)) {
curr += size + offset;
}
}
if (start == range.end - 1 and lessThan(items[start], value)) {
start += 1;
}
return start;
return curr;
}
fn binaryLast(comptime T: type, items: []T, value: T, range: Range, lessThan: fn (T, T) bool) usize {
var start = range.start;
var end = range.end - 1;
var curr = range.start;
var size = range.length();
if (range.start >= range.end) return range.end;
while (start < end) {
const mid = start + (end - start) / 2;
if (!lessThan(value, items[mid])) {
start = mid + 1;
} else {
end = mid;
while (size > 0) {
const offset = size % 2;
size /= 2;
const mid = items[curr + size];
if (!lessThan(value, mid)) {
curr += size + offset;
}
}
if (start == range.end - 1 and !lessThan(value, items[start])) {
start += 1;
}
return start;
return curr;
}
fn mergeInto(comptime T: type, from: []T, A: Range, B: Range, lessThan: fn (T, T) bool, into: []T) void {