SOURCE

// while实现
function dichotomy (numlist, value) {
    let min = 0
    let max = numlist.length - 1

    while(min <= max) {
        let middleIndex = parseInt((min + max) / 2)
        let item = numlist[middleIndex]
        if (item === value) {
            return middleIndex
        } else if (item > value) {
            max = middleIndex - 1
        } else if (item < value) {
            min = middleIndex + 1
        } else {
          return -1
        }
    }
}

// 递归实现
function recurrence (numlist, value, min = 0, max = numlist.length - 1 ) {
    let middleIndex = parseInt((min + max) / 2)
    let item = numlist[middleIndex]

    if (item === value) {
        return middleIndex
    } else if (item > value) {
        max = middleIndex - 1
       return recurrence(numlist, value, min, max )
    } else if (item < value) {
        min = middleIndex + 1
       return recurrence(numlist, value, min, max)
    } else {
        return -1
    }
}


console.log(dichotomy([1,2,3,4,5,6,7], 7))

console.log(recurrence([1,2,3,4,5,6,7], 5))