遞歸實現(xiàn)
const list = [11, 12, 13, 14, 17]
function get12(arr, start, end, num) {
console.log(arr, start, end, num)
const mid = Math.floor((start + end) / 2) // Math.floor
if (start > end) {
return null
}
if (arr[mid] === num) {
return mid
}
if (arr[mid] < num) {
return get12(arr, mid + 1, end, num) // mid + 1
}
if (arr[mid] > num) {
return get12(arr, start, mid - 1, num)
}
}
console.log(get12(list, 0, list.length - 1, 17))
while實現(xiàn)
const list = [11, 12, 13, 18, 19]
function get12(arr, num) {
let start = 0
let end = arr.length - 1
while(start <= end) {
const mid = Math.floor((end + start) / 2) // Math.floor
if (arr[mid] === num) {
return mid
}
if (arr[mid] < num) {
start = mid + 1 // mid + 1
}
if (arr[mid] > num) {
end = mid - 1 // mid - 1
}
}
return null
}
const l = console.log
l(get12(list, 19))
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