以下為javascript實(shí)現(xiàn)二分查找（binary search）的四種實(shí)現(xiàn)方式，其中第一種為遞歸寫(xiě)法，其他三種為迭代寫(xiě)法。

遞歸寫(xiě)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;
};

迭代寫(xiě)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;
};

迭代寫(xiě)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;
};