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34 lines
765 B
34 lines
765 B
// File: 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_searching
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/* 方法一：暴力列舉 */
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func twoSumBruteForce(nums []int, target int) []int {
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size := len(nums)
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// 兩層迴圈，時間複雜度為 O(n^2)
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for i := 0; i < size-1; i++ {
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for j := i + 1; j < 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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/* 方法二：輔助雜湊表 */
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func twoSumHashTable(nums []int, target int) []int {
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// 輔助雜湊表，空間複雜度為 O(n)
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hashTable := map[int]int{}
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// 單層迴圈，時間複雜度為 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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