以下为javascript实现二分查找（binary search）的四种实现方式，其中第一种为递归写法，其他三种为迭代写法。
递归写法(recursive approach)
const binarySearchRecursive = (nums, left, right, target) {
if (right <= left) {
return -1;
}
const mid = left + Math.floor((right - left) / 2);
if (nums[mid] > target) {
return binarySearchRecursive(nums, left, mid - 1, target);
} else if (nums[mid] < target) {
return binarySearchRecursive(nums, mid + 1, right, target);
}
return mid;
};
迭代写法1：left <= right
const binarySearchIterative1 = (nums, target) => {
let left = 0, right = nums.length - 1;
while (left <= right) {
const mid = left + Math.floor((right - left) / 2);
if (nums[mid] === target) {
return mid;
}
if (nums[mid] > target) {
right = mid - 1;
} else {
left = mid + 1;
}
}
return -1;
};
迭代写法2： left < right
const binarySearchIterative2 = (nums, target) => {
let left = 0, right = nums.length;
while (left < right) {
const mid = left + Math.floor((right - left) / 2);
if (nums[mid] === target) {
return mid;
}
if (nums[mid] > target) {
right = mid;
} else {
left = mid + 1;
}
}
return -1;
};
