Golang map 常用方法

前言

由于map是无序的，所以排序成 slice 返回，且都使用泛,代码只是示例，省略了错误判断

按key排序

package mainimport "fmt"func example[T comparable, S any](source map[T]S, assert func(a, b T) bool) []S {var (i []Tj []S)for k, _ := range source {i = append(i, k)}result := sort(i, assert)for _, k := range result {j = append(j, source[k])}return j
}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() {s := example(map[int]string{2: "b", 1: "a", 3: "c"}, func(a, b int) bool {return a > b})fmt.Println(s) //[c,b,a]
}

按value排序

package mainimport "fmt"func example[T comparable, S any](source map[T]S, assert func(a, b S) bool) []S {var (i []S)for _, v := range source {i = append(i, v)}return sort(i, assert)
}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() {s := example(map[int]int{3: 2, 2: 1, 1: 3}, func(a, b int) bool {return a > b})fmt.Println(s)
}

统计字符串中元素重复出现次数并将结果排序返回

package mainimport "fmt"type count struct {value stringcount int
}func example(s string) []count {var countSlice []countm := make(map[string]int, len(s))for _, char := range s {m[string(char)]++}for k, v := range m {countSlice = append(countSlice, count{count: v, value: k})}return sort(countSlice, func(a, b count) bool {return a.count > b.count})
}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() {s := example("abaabccccc")fmt.Println(s) //[{b 2} {a 3} {c 5}]
}