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来源：stackoverflow
2024-04-20 13:42:36
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问题内容
我试图用 go 解决 leetcode 问题。问题是子集。
这是我正在编写的完整代码以及一些调试日志：
package main
import (
"fmt"
)
func main() {
v := []int{9, 0, 3, 5, 7}
fmt.println(subsets(v))
}
func subsets(nums []int) [][]int {
result := [][]int{
[]int{}, // empty
}
for _, num := range nums {
fmt.println("==========")
fmt.println(num)
fmt.printf("result = %v\n", result)
temp := [][]int{}
for _, r := range result {
fmt.printf("r = %v\n", r)
temp = append(temp, append(r, num))
}
for _, t := range temp {
result = append(result, t)
}
fmt.println("==========")
}
return result
}
（我还准备了go游乐场网址）
这是上面代码的输出：
========== 9 result = [[]] r = [] ========== ========== 0 result = [[] [9]] r = [] r = [9] ========== ========== 3 result = [[] [9] [0] [9 0]] r = [] r = [9] r = [0] r = [9 0] ========== ========== 5 result = [[] [9] [0] [9 0] [3] [9 3] [0 3] [9 0 3]] r = [] r = [9] r = [0] r = [9 0] r = [3] r = [9 3] r = [0 3] r = [9 0 3] ========== ========== 7 result = [[] [9] [0] [9 0] [3] [9 3] [0 3] [9 0 3] [5] [9 5] [0 5] [9 0 5] [3 5] [9 3 5] [0 3 5] [9 0 3 5]] // (a) r = [] r = [9] r = [0] r = [9 0] r = [3] r = [9 3] r = [0 3] r = [9 0 3] r = [5] r = [9 5] r = [0 5] r = [9 0 5] r = [3 5] r = [9 3 5] r = [0 3 5] r = [9 0 3 7] // (b) ========== [[] [9] [0] [9 0] [3] [9 3] [0 3] [9 0 3] [5] [9 5] [0 5] [9 0 5] [3 5] [9 3 5] [0 3 5] [9 0 3 7] [7] [9 7] [0 7] [9 0 7] [3 7] [9 3 7] [0 3 7] [9 0 3 7] [5 7] [9 5 7] [0 5 7] [9 0 5 7] [3 5 7] [9 3 5 7] [0 3 5 7] [9 0 3 7 7]]
让我们看看第五个 result。 （我在那里指出了 (a) ）到目前为止， result 的最后一个元素是 [9, 0, 3, 5] ，这是预期的行为。 但是，之后，当我尝试在 result 中写入该元素的调试日志时，它会更改为 [9, 0, 3, 7] ( (b) )。
你知道为什么吗？
解决方案
append 在需要时更改 r：
而不是：
temp = append(temp, append(r, num))
您可以使用：
rr := make([]int, len(r))
copy(rr, r)
rr = append(rr, num)
temp = append(temp, rr)
你就可以开始了：
package main
import (
"fmt"
)
func main() {
v := []int{9, 0, 3, 5, 7}
fmt.println(subsets(v))
}
func subsets(nums []int) [][]int {
result := [][]int{
[]int{}, // empty
}
for _, num := range nums {
fmt.println("==========")
fmt.println(num)
fmt.printf("result = %v\n", result)
temp := [][]int{}
for _, r := range result {
fmt.printf("r = %v\n", r)
// append(r, num)
rr := make([]int, len(r))
copy(rr, r)
rr = append(rr, num)
temp = append(temp, rr)
}
for _, t := range temp {
result = append(result, t)
}
fmt.println("==========")
}
return result
}
只需调试您的代码，您就会看到，它发生在这里：
temp := [][]int{}
for _, r := range result {
fmt.println("result =", result, len(result), cap(result))
fmt.println("r ==", r, len(r), cap(r))
fmt.println("num =", num)
rr := append(r, num)
fmt.println("r ==", r, len(r), cap(r))
fmt.println("rr ==", rr, len(rr), cap(rr))
fmt.println("result =", result, len(result), cap(result))
fmt.println("temp =", temp)
temp = append(temp, rr)
fmt.println("temp =", temp)
}
什么时候
result = [[] [9] [0] [9 0] [3] [9 3] [0 3] [9 0 3] [5] [9 5] [0 5] [9 0 5] [3 5] [9 3 5] [0 3 5] [9 0 3 5]] 16 16 r == [9 0 3] 3 4 num = 7 r == [9 0 3] 3 4 rr == [9 0 3 7] 4 4 result = [[] [9] [0] [9 0] [3] [9 3] [0 3] [9 0 3] [5] [9 5] [0 5] [9 0 5] [3 5] [9 3 5] [0 3 5] [9 0 3 7]] 16 16
因为：
append(r, num)
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