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Commit 81dc774

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[新增] 新增题目 704. 二分查找
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‎src/704_binarySearch.ts‎

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import testCases from '../tests/testCases/704_binarySearch'
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/*
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704. 二分查找
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https://leetcode.cn/problems/binary-search/
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难度:简单
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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。
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示例 1:
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输入: nums = [-1,0,3,5,9,12], target = 9
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输出: 4
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解释: 9 出现在 nums 中并且下标为 4
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示例 2:
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输入: nums = [-1,0,3,5,9,12], target = 2
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输出: -1
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解释: 2 不存在 nums 中因此返回 -1
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提示:
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你可以假设 nums 中的所有元素是不重复的。
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n 将在 [1, 10000]之间。
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nums 的每个元素都将在 [-9999, 9999]之间。
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*/
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/**
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* 二分查找元素下标
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* - LeetCode 入口
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* @param nums - 待查找的整型数组,要求为升序且没有重复元素
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* @param target - 待查找的数字
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* @returns {number} 元素下标
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*/
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function search (nums: number[], target: number): number {
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// 使用左右指针,每次查找 [left, right) 最中间的值
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let left = 0
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let right = nums.length
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while (left < right) {
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// 使用位运算获取左右中间的下标,位运算 >> 1 等同于 Math.floor()
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const middle = left + ((right - left) >> 1)
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// 要查找的目标为当前正中间的元素,返回正中间的下标
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if (target === nums[middle]) return middle
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// 要查找的目标大于当前正中间的元素,将查找区间更新为右区间
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if (target > nums[middle]) left = middle + 1
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// 要查找的目标小于当前正中间的元素,将查找区间更新为左区间
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if (target < nums[middle]) right = middle
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}
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// 没有查找到对应的元素
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return -1
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}
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// Debug
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if (require.main === module) {
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const { input, expected } = testCases[6]
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const output = search(input.nums, input.target)
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console.log({ input, output, expected })
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}
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export { search }

‎tests/704_binarySearch.test.ts‎

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import { describe, test, expect } from '@jest/globals'
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import testCases from './testCases/704_binarySearch'
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import { search } from '../src/704_binarySearch'
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describe('704. Binary Search', () => {
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testCases.forEach(({ input, expected }, index) => {
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test(`Test case index: ${index}`, () => {
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expect(search(input.nums, input.target)).toBe(expected)
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})
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})
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})

‎tests/testCases/704_binarySearch.ts‎

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export default [
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{
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input: {
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nums: [-1, 0, 3, 5, 9, 12],
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target: -1
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},
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expected: 0
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},
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{
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input: {
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nums: [-1, 0, 3, 5, 9, 12],
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target: 0
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},
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expected: 1
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},
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{
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input: {
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nums: [-1, 0, 3, 5, 9, 12],
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target: 3
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},
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expected: 2
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},
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{
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input: {
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nums: [-1, 0, 3, 5, 9, 12],
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target: 5
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},
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expected: 3
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},
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{
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input: {
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nums: [-1, 0, 3, 5, 9, 12],
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target: 9
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},
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expected: 4
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},
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{
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input: {
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nums: [-1, 0, 3, 5, 9, 12],
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target: 12
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},
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expected: 5
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},
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{
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input: {
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nums: [-1, 0, 3, 5, 9, 12],
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target: 2
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},
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expected: -1
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}
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]

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