34 lines
754 B
Go
34 lines
754 B
Go
// File: leetcode_two_sum.go
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// Created Time: 2022-11-25
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// Author: reanon (793584285@qq.com)
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package chapter_computational_complexity
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// twoSumBruteForce
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func twoSumBruteForce(nums []int, target int) []int {
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size := len(nums)
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// 两层循环，时间复杂度 O(n^2)
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for i := 0; i < size-1; i++ {
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for j := i + 1; i < size; j++ {
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if nums[i]+nums[j] == target {
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return []int{i, j}
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}
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}
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}
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return nil
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}
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// twoSumHashTable
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func twoSumHashTable(nums []int, target int) []int {
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// 辅助哈希表，空间复杂度 O(n)
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hashTable := map[int]int{}
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// 单层循环，时间复杂度 O(n)
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for idx, val := range nums {
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if preIdx, ok := hashTable[target-val]; ok {
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return []int{preIdx, idx}
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}
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hashTable[val] = idx
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}
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return nil
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}
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