我正在嘗試使用 Golang 解決一些動(dòng)態(tài)編程問(wèn)題。我寫了一個(gè)函數(shù)func main() { fmt.Println(HowSum(5, []int{1, 2, 5}))}func HowSum(targetNum int, numbers []int) []int { retAry = make([][]int, targetNum+1) retAry[0] = make([]int, 0) for i := 0; i <= targetNum; i++ { if retAry[i] != nil { for _, num := range numbers { if i+num <= targetNum { fmt.Print("Before:", i, " round, num =", num, retAry, "\n") retAry[i+num] = append(retAry[i], num) fmt.Print("After :", i, " round, num =", num, retAry, "\n\n") } } } } return retAry[targetNum]}部分結(jié)果如下。...Before:3 round, num =2 [[] [1] [1 1] [1 1 1] [1 1 1 1] [5]]After :3 round, num =2 [[] [1] [1 1] [1 1 1] [1 1 1 2] [1 1 1 2]]...[1 1 1 2 1]當(dāng)程序?qū)?retAry[5] 從 [5] 替換為 [1 1 1 2] 時(shí)，retAry[4] 中的數(shù)組從 [1 1 1 1] 更改為 [1 1 1 2]。發(fā)生什么事？但是，如果替換 retAry[i+num] = append(retAry[i], num)為retAry[i+num] = append([]int{num}, retAry[i]...)，我可以得到正確的答案。...Before:3 round, num =2 [[] [1] [1 1] [1 1 1] [1 1 1 1] [5]]After :3 round, num =2 [[] [1] [1 1] [1 1 1] [1 1 1 1] [2 1 1 1]]...[1 1 1 1 1]誰(shuí)能幫助解釋我犯了什么錯(cuò)誤？代碼在這里
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海綿寶寶撒
TA貢獻(xiàn)1809條經(jīng)驗(yàn) 獲得超8個(gè)贊
However, if replace retAry[i+num] = append(retAry[i], num) to retAry[i+num] = append([]int{num}, retAry[i]...) , I can get the correct answer.
解釋：
retAry[i+num] = append(retAry[i], num)在 retAry[i+num] 和 retAry[i] 之間共享相同的數(shù)組。如果您修改一個(gè)切片，則其他切片也可以更改。
func main() {
s1 := append([]int{}, 1, 2, 3) // len: 3, cap 4 []int{1, 2, 3, 0}
// it appends 4 to 4th index and assign new slice to s2.
// s2 is share the same array with s1
// s1 : len: 3, cap 4 []int{1, 2, 3, 4}
// s2 : len: 4, cap 4 []int{1, 2, 3, 4}
s2 := append(s1, 4)
// s3 is share the same array with s1 and s2 as well
// when you append 4th index to s1, and assign to s3, both s1 and s2 will change as well
// s1 : len: 3, cap 4 []int{1, 2, 3, 5}
// s2 : len: 4, cap 4 []int{1, 2, 3, 5}
// s3 : len: 4, cap 4 []int{1, 2, 3, 5}
s3:= append(s1, 5)
fmt.Println(s2, s3) // output [1 2 3 5] [1 2 3 5]
}
retAry[i+num] = append([]int{num}, retAry[i]...)
[]int{num}您使用新數(shù)組初始化新切片，然后將 retAry[i] 中的每個(gè)元素附加到新數(shù)組。它們不再是 retAry[i+num] 和 retAry[i] 之間的任何引用。
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