hello-algo/codes/swift/chapter_searching/two_sum.swift
Yudong Jin e720aa2d24
feat: Revised the book (#978)
* Sync recent changes to the revised Word.

* Revised the preface chapter

* Revised the introduction chapter

* Revised the computation complexity chapter

* Revised the chapter data structure

* Revised the chapter array and linked list

* Revised the chapter stack and queue

* Revised the chapter hashing

* Revised the chapter tree

* Revised the chapter heap

* Revised the chapter graph

* Revised the chapter searching

* Reivised the sorting chapter

* Revised the divide and conquer chapter

* Revised the chapter backtacking

* Revised the DP chapter

* Revised the greedy chapter

* Revised the appendix chapter

* Revised the preface chapter doubly

* Revised the figures
2023-12-02 06:21:34 +08:00

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/**
* File: two_sum.swift
* Created Time: 2023-01-03
* Author: nuomi1 (nuomi1@qq.com)
*/
/* */
func twoSumBruteForce(nums: [Int], target: Int) -> [Int] {
// O(n^2)
for i in nums.indices.dropLast() {
for j in nums.indices.dropFirst(i + 1) {
if nums[i] + nums[j] == target {
return [i, j]
}
}
}
return [0]
}
/* */
func twoSumHashTable(nums: [Int], target: Int) -> [Int] {
// O(n)
var dic: [Int: Int] = [:]
// O(n)
for i in nums.indices {
if let j = dic[target - nums[i]] {
return [j, i]
}
dic[nums[i]] = i
}
return [0]
}
@main
enum LeetcodeTwoSum {
/* Driver Code */
static func main() {
// ======= Test Case =======
let nums = [2, 7, 11, 15]
let target = 13
// ====== Driver Code ======
//
var res = twoSumBruteForce(nums: nums, target: target)
print("方法一 res = \(res)")
//
res = twoSumHashTable(nums: nums, target: target)
print("方法二 res = \(res)")
}
}