LeetCode 「简单」704.二分查找
题目描述
给定一个 n 个元素有序的（升序）整型数组 nums 和一个目标值 target ，写一个函数搜索 nums 中的 target，如果目标值存在返回下标，否则返回 -1。
示例
输入：nums = [-1,0,3,5,9,12], target = 9
输出：4
输入：nums = [-1,0,3,5,9,12], target = 2
输出：-1
解答
递归
Code
/**
* @param {number[]} nums
* @param {number} target
* @return {number}
*/
var search = function(nums, target) {
var partition = function(nums, left, right, target) {
if (left > right) return -1;
const mid = Math.floor((right + left) / 2);
if (nums[mid] === target) return mid;
else if (nums[mid] > target) return partition(nums, left, mid - 1, target);
else return partition(nums, mid + 1, right, target);
};
return partition(nums, 0, nums.length - 1, target);
};
非递归实现
Code
var search = function(nums, target) {
let left = 0, right = nums.length - 1;
while (left <= right) {
const mid = Math.floor((left + right) / 2);
if (nums[mid] === target) return mid;
else if (nums[mid] > target) right = mid - 1;
else left = mid + 1;
}
return -1;
};