二分查找（闭区间）

递归写法

let binarySearch_recursion = function(nums, target, left = 0, right = nums.length - 1) {
    if(left > right) return -1
    let mid = Math.floor((right + left) / 2)
    if(nums[mid] == target) {
        return mid
    }else if(nums[mid] < target) {
        return binarySearch_recursion(nums, target, mid + 1, right)
    }else {
        return binarySearch_recursion(nums, target, left, mid - 1)
    }
}
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迭代写法

let binarySearch = function(nums, target, left = 0, right = nums.length - 1){
    if(left > right) return -1
    while(left <= right) {
        let mid = left + ((right - left) >> 1)
        if(nums[mid] == target) {
            return mid
        }else if(nums[mid] < target) {
            left = mid + 1
        }else {
            right = mid - 1
        }
    }
    return left
}
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