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ExponentialSearch.js

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/**

* Exponential Search

*

* The algorithm consists of two stages. The first stage determines a

* range in which the search key would reside if it were in the list.

* In the second stage, a binary search is performed on this range.

*

*

*

*/

function binarySearch(arr, value, floor, ceiling) {

// Middle index

const mid = Math.floor((floor + ceiling) / 2)

// If value is at the mid position return this position

if (arr[mid] === value) {

return mid

}

if (floor > ceiling) return -1

// If the middle element is great than the value

// search the left part of the array

if (arr[mid] > value) {

return binarySearch(arr, value, floor, mid - 1)

// If the middle element is lower than the value

// search the right part of the array

} else {

return binarySearch(arr, value, mid + 1, ceiling)

}

}

function exponentialSearch(arr, length, value) {

// If value is the first element of the array return this position

if (arr[0] === value) {

return 0

}

// Find range for binary search

let i = 1

while (i < length && arr[i] <= value) {

i = i * 2

}

// Call binary search for the range found above

return binarySearch(arr, value, i / 2, Math.min(i, length))

}

export { binarySearch, exponentialSearch }

// const arr = [2, 3, 4, 10, 40, 65, 78, 100]

// const value = 78

// const result = exponentialSearch(arr, arr.length, value)