手写题

1.使用js实现二分查找

// 非递归的方式
function search(arr, key) {
            var start = 0;
            var end = arr.length - 1
            while (start <= end) {
                var mid = parseInt((start + end) / 2)
                if (key === arr[mid]) {
                    return mid
                } else if (key > arr[mid]) {
                    start = mid + 1
                } else {
                    end = mid - 1
                }
            }
            return -1
        }var arr = [0, 13, 21, 35, 46, 52, 68, 77, 89, 94];
        console.log(search2(arr, 94)); 

// 递归的方式
function search2(arr, key, start = 0, end = arr.length - 1) {
            var mid = parseInt((start + end) / 2)
            if (key > arr[mid]) {
                return search2(arr, key, mid + 1, end)
            } else if (key < arr[mid]) {
                return search2(arr, key, start, mid - 1)
            } else if (key === arr[mid]) {
                return mid
            } else {
                return -1
            }
        }

 var arr = [0, 13, 21, 35, 46, 52, 68, 77, 89, 94];
 console.log(search2(arr, 94));