binary search implementation on golang slices

golang_binary_search.go

package main

import (
	"fmt"
)

func BinarySearch(target_map []int, value int) int {

	start_index := 0
	end_index := len(target_map) - 1

	for start_index <= end_index {

		median := (start_index + end_index) / 2

		if target_map[median] < value {
			start_index = median + 1
		} else {
			end_index = median - 1
		}

	}

	if start_index == len(target_map) || target_map[start_index] != value {
		return -1
	} else {
		return start_index
	}

}

func main() {

	values := []int{1, 2, 3, 4, 5, 6, 7}
	fmt.Println(BinarySearch(values, 5))

}

1. That's a slice not a map
2. if you're using slices, why not use the built-in sort.Search() ?

1. That's a slice not a map

Fixed. I don't know what was I thinking.

2. if you're using slices, why not use the built-in sort.Search() ?

I was just practicing golang.

In the 14th-row, I think we should improve a little bit to avoid memory overflow:

median := start_index + (end_index - start_index) / 2

I think this is simpler but not sure if it's correct (untested):

start_index := 0
end_index := len(target_map)

for start_index < end_index {
	median := start_index + (end_index - start_index) / 2
	if target_map[start_index] == value {
		return start_index
	}
	if target_map[median] < value {
		start_index = median
	} else {
		end_index = median
	}
}

return -1

./main.go:19:4: too many arguments to return

I think this is simpler but not sure if it's correct (untested):

start_index := 0
end_index := len(target_map)

for start_index < end_index {
	median := start_index + (end_index - start_index) / 2
	if target_map[start_index] == value {
		return start_index
	}
	if target_map[median] < value {
		start_index = median
	} else {
		end_index = median
	}
}

return -1

./main.go:19:4: too many arguments to return

func binarySearch(arr []int, val int) int {
	first := 0
	last := len(arr) - 1

	for first <= last {
		mid := (first + last) / 2
		switch {
		case arr[mid] == val:
			return mid
		case arr[mid] < val:
			first = mid + 1
		case arr[mid] > val:
			last = mid - 1
		}
	}
	return -1
}

You can additionally add validation in case if array of given elements is not sorted for sure

if !sort.IntsAreSorted(target_map) { panic("Given array is not sorted") }