Golang 切片 常用方法

下面的方法省略一些校验，如数组越界等，且都采用泛型(要求go版本 >= 1.18)

移除指定位置的元素

package mainimport ("fmt"
)func Delete[T any](source []T, index int) []T {return append(source[:index], source[index+1:]...)
}func main() {fmt.Println(Delete([]int{1, 2, 3, 4, 5}, 3)) //[1,2,3,5]
}

查找元素的位置

找到返回位置，找不到返回 -1
也可以用来判断某个元素是否存在，大于 -1 即存在

package mainimport ("fmt"
)func Delete[T any](source []T, assert func(t T) bool) int {for index, item := range source {if assert(item) {return index}}return -1
}func main() {fmt.Println(Delete([]int{1, 2, 3, 4, 5}, func(t int) bool {return t == 3}))// 2
}

查找最大最小的元素

package mainimport ("fmt"
)func Find[T any](source []T, assert func(t1, t2 T) bool) T {max := source[0]for _, item := range source {if assert(max, item) {max = item}}return max
}func main() {fmt.Println(Find([]int{1, 2, 22, 8, 11, 3, 4, 5}, func(t1, t2 int) bool {return t2 > t1})) //22fmt.Println(Find([]int{1, 2, 22, 8, 11, 3, 4, 5}, func(t1, t2 int) bool {return t2 < t1})) //1
}

去重

T 使用 comparable 是因为 map 需要一个可比较的类型

package mainimport "fmt"func Uniq[T comparable](collection []T) []T {result := make([]T, 0, len(collection))seen := make(map[T]struct{}, len(collection))for _, item := range collection {if _, ok := seen[item]; ok {continue}seen[item] = struct{}{}result = append(result, item)}return result
}func main() {fmt.Println(Uniq([]int{6, 7, 6, 5})) //[6,7,5]
}

使用 struct{}{} 是因为它不占内存

package mainfunc main() {fmt.Println(unsafe.Sizeof(struct{}{})) // 0fmt.Println(unsafe.Sizeof(true))       // 1
}

随机打乱

这里引入了 i int64，这个是让他们的随机种子不一样，不然在 main中的 10次打印结果都一致

package mainimport ("fmt""math/rand""time"
)func random[T any](input []T, i int64) []T {rand.Seed(time.Now().Unix() + i)for i := len(input) - 1; i >= 0; i-- {index := rand.Intn(i + 1)input[index], input[i] = input[i], input[index]}return input
}func main() {for i := 0; i < 10; i++ {fmt.Println(random([]int{1, 2, 3, 4, 5, 6, 7, 8, 9}, int64(i)))}//下面的结果都一样for i := 0; i < 10; i++ {fmt.Println(random([]int{1, 2, 3, 4, 5, 6, 7, 8, 9}, 0))}
}

排序

这里展示的是选择排序，可以更换其它排序算法

package mainimport "fmt"func sort[T any](source []T, assert func(a, b T) bool) []T {for i := 0; i < len(source); i++ {for j := i + 1; j < len(source); j++ {if assert(source[i], source[j]) {source[j], source[i] = source[i], source[j]}}}return source
}func main() {r := sort([]int{1, 4, 3, 9, 7, 8, 5}, func(a, b int) bool {return a < b})fmt.Println(r) //[9 8 7 5 4 3 1]
}

二维排序

在排序的基础上增加了一个 index(要比较的元素位置)，根据二维index位置的元素大小，来决定一维的排序位置

package mainimport "fmt"func TwoDimensionalSort[T any](source [][]T, index int, assert func(a, b T) bool) [][]T {for i := 0; i < len(source); i++ {for j := i + 1; j < len(source); j++ {//二维index位置上元素的比较if assert(source[i][index], source[j][index]) {//一维位置交换source[j], source[i] = source[i], source[j]}}}return source
}func main() {result := TwoDimensionalSort([][]int{{1, 3, 5}, {6, 2, 3}, {5, 9, 1}}, 2, func(a, b int) bool {return a > b})fmt.Println(result) //[[5 9 1] [6 2 3] [1 3 5]]result = TwoDimensionalSort([][]int{{1, 3, 5}, {6, 2, 3}, {5, 9, 1}}, 1, func(a, b int) bool {return a > b})fmt.Println(result) //[[6 2 3] [1 3 5] [5 9 1]]
}

sort.Sort 排序

进阶版本使用泛型加 sor.Sort 处理，算法由 sort.Sort 实现，而我只需要实现它排序对象的接口即可,Len()返回元素数量，Less() 比较方式 i 是否要 排在 j 前面，Swap() 交换方式

type Interface interface {// Len is the number of elements in the collection.Len() int// Less reports whether the element with index i// must sort before the element with index j.//// If both Less(i, j) and Less(j, i) are false,// then the elements at index i and j are considered equal.// Sort may place equal elements in any order in the final result,// while Stable preserves the original input order of equal elements.//// Less must describe a transitive ordering://  - if both Less(i, j) and Less(j, k) are true, then Less(i, k) must be true as well.//  - if both Less(i, j) and Less(j, k) are false, then Less(i, k) must be false as well.//// Note that floating-point comparison (the < operator on float32 or float64 values)// is not a transitive ordering when not-a-number (NaN) values are involved.// See Float64Slice.Less for a correct implementation for floating-point values.Less(i, j int) bool// Swap swaps the elements with indexes i and j.Swap(i, j int)
}

package mainimport ("fmt""sort"
)type SortStruct[T comparable] struct {Data   [][]TAssert func(a, b T) boolIndex  int
}func (s SortStruct[T]) Len() int {return len(s.Data)
}func (s SortStruct[T]) Less(i, j int) bool {return s.Assert(s.Data[i][s.Index], s.Data[j][s.Index])
}func (s SortStruct[T]) Swap(i, j int) {s.Data[i], s.Data[j] = s.Data[j], s.Data[i]
}func main() {result := SortStruct[int]{Data: [][]int{{1, 2, 3},{3, 1, 2},{6, 7, 8},},Assert: func(a, b int) bool {return a < b},Index: 1,}sort.Sort(result)fmt.Println(result.Data) //[[3 1 2] [1 2 3] [6 7 8]]
}