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refactor: make BinarySearch func code clear

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dudaodong
2022-01-21 11:57:36 +08:00
parent bd30855ae6
commit 3f8effb7a3
1 changed files with 17 additions and 10 deletions
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27
algorithm/search.go
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@@ -6,6 +6,8 @@ package algorithm
import "github.com/duke-git/lancet/lancetconstraints" import "github.com/duke-git/lancet/lancetconstraints"
// Search algorithms see https://github.com/TheAlgorithms/Go/tree/master/search
// LinearSearch Simple linear search algorithm that iterates over all elements of an slice // LinearSearch Simple linear search algorithm that iterates over all elements of an slice
// If a target is found, the index of the target is returned. Else the function return -1 // If a target is found, the index of the target is returned. Else the function return -1
func LinearSearch[T any](slice []T, target T, comparator lancetconstraints.Comparator) int { func LinearSearch[T any](slice []T, target T, comparator lancetconstraints.Comparator) int {
@@ -19,17 +21,19 @@ func LinearSearch[T any](slice []T, target T, comparator lancetconstraints.Compa
// BinarySearch search for target within a sorted slice, recursive call itself. // BinarySearch search for target within a sorted slice, recursive call itself.
// If a target is found, the index of the target is returned. Else the function return -1 // If a target is found, the index of the target is returned. Else the function return -1
func BinarySearch[T any](slice []T, target T, lowIndex, highIndex int, comparator lancetconstraints.Comparator) int { func BinarySearch[T any](sortedSlice []T, target T, lowIndex, highIndex int, comparator lancetconstraints.Comparator) int {
if highIndex < lowIndex || len(slice) == 0 { if highIndex < lowIndex || len(sortedSlice) == 0 {
return -1 return -1
} }
midIndex := int(lowIndex + (highIndex-lowIndex)/2) midIndex := int(lowIndex + (highIndex-lowIndex)/2)
// slice[midIndex] > target isMidValGreatTarget := comparator.Compare(sortedSlice[midIndex], target) == 1
if comparator.Compare(slice[midIndex], target) == 1 { isMidValLessTarget := comparator.Compare(sortedSlice[midIndex], target) == -1
return BinarySearch(slice, target, lowIndex, midIndex-1, comparator)
} else if comparator.Compare(slice[midIndex], target) == -1 { if isMidValGreatTarget {
return BinarySearch(slice, target, midIndex+1, highIndex, comparator) return BinarySearch(sortedSlice, target, lowIndex, midIndex-1, comparator)
} else if isMidValLessTarget {
return BinarySearch(sortedSlice, target, midIndex+1, highIndex, comparator)
} }
return midIndex return midIndex
@@ -37,16 +41,19 @@ func BinarySearch[T any](slice []T, target T, lowIndex, highIndex int, comparato
// BinaryIterativeSearch search for target within a sorted slice. // BinaryIterativeSearch search for target within a sorted slice.
// If a target is found, the index of the target is returned. Else the function return -1 // If a target is found, the index of the target is returned. Else the function return -1
func BinaryIterativeSearch[T any](slice []T, target T, lowIndex, highIndex int, comparator lancetconstraints.Comparator) int { func BinaryIterativeSearch[T any](sortedSlice []T, target T, lowIndex, highIndex int, comparator lancetconstraints.Comparator) int {
startIndex := lowIndex startIndex := lowIndex
endIndex := highIndex endIndex := highIndex
var midIndex int var midIndex int
for startIndex <= endIndex { for startIndex <= endIndex {
midIndex = int(startIndex + (endIndex-startIndex)/2) midIndex = int(startIndex + (endIndex-startIndex)/2)
if comparator.Compare(slice[midIndex], target) == 1 { isMidValGreatTarget := comparator.Compare(sortedSlice[midIndex], target) == 1
isMidValLessTarget := comparator.Compare(sortedSlice[midIndex], target) == -1
if isMidValGreatTarget {
endIndex = midIndex - 1 endIndex = midIndex - 1
} else if comparator.Compare(slice[midIndex], target) == -1 { } else if isMidValLessTarget {
startIndex = midIndex + 1 startIndex = midIndex + 1
} else { } else {
return midIndex return midIndex