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feat(computational_complexity/two_sum): add go code #8

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1 change: 1 addition & 0 deletions .gitignore
Original file line number Diff line number Diff line change
Expand Up @@ -3,6 +3,7 @@

# Editor
.vscode/
.idea/

# mkdocs files
site/
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30 changes: 30 additions & 0 deletions codes/go/chapter_computational_complexity/leetcode_two_sum.go
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@@ -0,0 +1,30 @@
// File: leetcode_two_sum.go
// Created Time: 2022-11-25
// Author: reanon (793584285@qq.com)

package chapter_computational_complexity

// twoSumBruteForce
func twoSumBruteForce(nums []int, target int) []int {
size := len(nums)
for i := 0; i < size-1; i++ {
for j := i + 1; i < size; j++ {
if nums[i]+nums[j] == target {
return []int{i, j}
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}
}
}
return nil
}

// twoSumHashTable
func twoSumHashTable(nums []int, target int) []int {
hashTable := map[int]int{}
for idx, val := range nums {
if preIdx, ok := hashTable[target-val]; ok {
return []int{preIdx, idx}
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}
hashTable[val] = idx
}
return nil
}
24 changes: 24 additions & 0 deletions codes/go/chapter_computational_complexity/leetcode_two_sum_test.go
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@@ -0,0 +1,24 @@
// File: leetcode_two_sum.go
// Created Time: 2022-11-25
// Author: reanon (793584285@qq.com)

package chapter_computational_complexity

import (
"testing"
)

func TestTwoSum(t *testing.T) {
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// ======= Test Case =======
nums := []int{2, 7, 11, 15}
target := 9

// ====== Driver Code ======
// 方法一:暴力解法
res := twoSumBruteForce(nums, target)
t.Log("brute force:", res)

// 方法二:哈希表
res = twoSumHashTable(nums, target)
t.Log("hash table:", res)
}
3 changes: 3 additions & 0 deletions codes/go/go.mod
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@@ -0,0 +1,3 @@
module github.com/krahets/hello-algo

go 1.19
37 changes: 35 additions & 2 deletions docs/chapter_computational_complexity/space_time_tradeoff.md
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Expand Up @@ -33,7 +33,7 @@
=== "C++"

```cpp title="leetcode_two_sum.cpp"

```

=== "Python"
Expand All @@ -42,6 +42,24 @@

```

=== "Go"

```go title="leetcode_two_sum.go"
func twoSum(nums []int, target int) []int {
size := len(nums)
for i := 0; i < size-1; i++ {
for j := i + 1; i < size; j++ {
if nums[i]+nums[j] == target {
return []int{i, j}
}
}
}
return nil
}
```



### 方法二:辅助哈希表

时间复杂度 $O(N)$ ,空间复杂度 $O(N)$ ,属于「空间换时间」。
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=== "C++"

```cpp title="leetcode_two_sum.cpp"

```

=== "Python"

```python title="leetcode_two_sum.py"

```

=== "Go"

```go title="leetcode_two_sum.go"
func twoSumHashTable(nums []int, target int) []int {
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hashTable := map[int]int{}
for idx, val := range nums {
if preIdx, ok := hashTable[target-val]; ok {
return []int{preIdx, idx}
}
hashTable[val] = idx
}
return nil
}
```