Golang Slice技巧

2,871

追加元素

``````a = append(a, b...)
``````

复制

``````b = make([]T, len(a))
copy(b,a)
// or
b = append([]T(nil), a...)
// or
b = append(a[:0:0], a...)
``````

裁剪

``````a = append(a[:i], a[j:]...)
``````

删除元素

``````a = append(a[:i], a[i+1:]...)
// or
a = a[:i+copy(a[i:], a[i+1:])]
``````

删除而不保留顺序

``````a[i] = a[len(a)-1]
a = a[:len(a)-1]
``````

裁剪

``````copy(a[i:], a[j:])
for k, n := len(a)-j+i, len(a); k < n; k++ {
a[k] = nil // or the zero value of T
}
a = a[:len(a)-j+i]
``````

删除

``````copy(a[i:], a[i+1:])
a[len(a)-1] = nil // or the zero value of T
a = a[:len(a)-1]
``````

删除不保留顺序

``````a[i] = a[len(a)-1]
a[len(a)-1] = nil
a = a[:len(a)-1]
``````

扩大

``````a = append(a[:i], append(make([]T, j), a[i:]...)...)
``````

延伸

``````a = append(a, make([]T, j)...)
``````

插入

``````a = append(a[:i], append([]T{x}, a[i:]...)...)
``````

插入

``````s = append(s, 0 /* use the zero value of the element type */)
copy(s[i+1:], s[i:])
s[i] = x
``````

插入Slice

``````a = append(a[:i], append(b, a[i:]...)...)
``````

增加元素

``````a = append(a, x)
``````

取出最后一个元素

``````x, a = a[len(a)-1], a[:len(a)-1]
``````

Push Front/Unshift

``````a = append([]T{x}, a...)
``````

Pop Front/Shift

``````x, a = a[0], a[1:]
``````

其他技巧

不进行内存分配过滤

``````b := a[:0]
for _, x := range a {
if f(x) {
b = append(b, x)
}
}
``````

``````for i := len(b); i < len(a); i++ {
a[i] = nil // or the zero value of T
}
``````

反转

``````for i := len(a)/2-1; i >= 0; i-- {
opp := len(a)-1-i
a[i], a[opp] = a[opp], a[i]
}

``````
``````for left, right := 0, len(a)-1; left < right; left, right = left+1, right-1 {
a[left], a[right] = a[right], a[left]
}
``````

打乱顺序

``````for i := len(a) - 1; i > 0; i-- {
j := rand.Intn(i + 1)
a[i], a[j] = a[j], a[i]
}
``````
``````words := strings.Fields("ink runs from the corners of my mouth")
rand.Shuffle(len(words), func(i, j int) {
words[i], words[j] = words[j], words[i]
})
fmt.Println(words)
``````

批处理

``````actions := []int{0, 1, 2, 3, 4, 5, 6, 7, 8, 9}
batchSize := 3
var batches [][]int

for batchSize < len(actions) {
actions, batches = actions[batchSize:], append(batches, actions[0:batchSize:batchSize])
}
batches = append(batches, actions)

output:
[[0 1 2] [3 4 5] [6 7 8] [9]]

``````

去重

``````import "sort"

in := []int{3,2,1,4,3,2,1,4,1} // any item can be sorted
sort.Ints(in)
j := 0
for i := 1; i < len(in); i++ {
if in[j] == in[i] {
continue
}
j++
// preserve the original data
// in[i], in[j] = in[j], in[i]
// only set what is required
in[j] = in[i]
}
result := in[:j+1]
fmt.Println(result) // [1 2 3 4]
``````