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main.go
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main.go
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package main
import (
"fmt"
)
func main() {
fmt.Println("main")
arr := []int{9, 9, 9}
n := 9
fmt.Printf("n - %v, arr - %v, idx - %v\n", n, arr, binarySearch(n, arr))
arr = []int{9, 19, 29}
n = 9
fmt.Printf("n - %v, arr - %v, idx - %v\n", n, arr, binarySearch(n, arr))
arr = []int{9, 19, 29}
n = 29
fmt.Printf("n - %v, arr - %v, idx - %v\n", n, arr, binarySearch(n, arr))
arr = []int{}
n = 9
fmt.Printf("n - %v, arr - %v, idx - %v\n", n, arr, binarySearch(n, arr))
arr = []int{1, 2, 3, 4}
n = 9
fmt.Printf("n - %v, arr - %v, idx - %v\n", n, arr, binarySearch(n, arr))
}
// cpu - O(logN);
// return index of search value n in array (sorted)
// if not found return len(arr)
// if found idx in range [0, len(arr))
func binarySearch(n int, arr []int) int {
// range index in array
i, j := 0, len(arr)
for i < j {
// get middle value by devide 2
// overflow posible
mid := int(uint(i+j) >> 1)
if !(arr[mid] >= n) {
i = mid + 1
} else {
j = mid
}
}
return i
}