mirror of
https://github.com/krahets/hello-algo.git
synced 2024-12-27 02:06:29 +08:00
46 lines
1.2 KiB
Swift
46 lines
1.2 KiB
Swift
/**
|
||
* File: leetcode_two_sum.swift
|
||
* Created Time: 2023-01-03
|
||
* Author: nuomi1 (nuomi1@qq.com)
|
||
*/
|
||
|
||
func twoSumBruteForce(nums: [Int], target: Int) -> [Int] {
|
||
// 两层循环，时间复杂度 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] {
|
||
// 辅助哈希表，空间复杂度 O(n)
|
||
var dic: [Int: Int] = [:]
|
||
// 单层循环，时间复杂度 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 {
|
||
static func main() {
|
||
// ======= Test Case =======
|
||
let nums = [2, 7, 11, 15]
|
||
let target = 9
|
||
// ====== Driver Code ======
|
||
// 方法一
|
||
var res = twoSumBruteForce(nums: nums, target: target)
|
||
print("方法一 res = \(res)")
|
||
// 方法二
|
||
res = twoSumHashTable(nums: nums, target: target)
|
||
print("方法二 res = \(res)")
|
||
}
|
||
}
|