整数スライスを整数スライスに追加すると、追加されるスライスが変更されます

Question

整数スライスを整数スライスに追加しようとしています。スライスを印刷すると、期待通りに表示されます。しかし、スライスをスライスのスライスに追加すると、コンテンツが変更されます。

package main 

import "fmt" 

var myGraph [8][8]bool //the graph 

var visited [8]bool //an array that marks if visited 

var path []int //a slice to store a possible path 

var paths [][]int 

func dfs(src int, dest int) { 
    //add current node to path 
    path = append(path, src) 

    //mark current node as visited 
    visited[src] = true 

    //if the current node is the destination 
    //print the path and return 
    if src == dest { 
     fmt.Println(path) 
     paths = append(paths, path) //I'm trying to push the path slice into the paths slice 
     return 
    } 

    for i := 1; i <= 7; i++ { //loop through all nodes 

     //if ith node is a neighbour of the current node and it is not visited 
     if myGraph[src][i] && visited[i] == false { 

      // call dfs on the current node 
      dfs(i, dest) 

      //mark the current node as unvisited 
      //so that we can other paths to the final destination 
      visited[i] = false 

      //re-slice the slice - get rid of the current node 
      path = path[:len(path)-1] 
     } 

    } 

} 

func main() { 
    path = make([]int, 0, 8) 
    paths = make([][]int, 0, 10) 

    //creating the graph 
    myGraph[1] = [...]bool{false, false, true, true, false, false, true, false} 
    myGraph[2] = [...]bool{false, true, false, true, false, true, false, false} 
    myGraph[3] = [...]bool{false, true, true, false, true, false, true, false} 
    myGraph[4] = [...]bool{false, false, false, true, false, false, true, false} 
    myGraph[5] = [...]bool{false, false, true, false, false, false, true, false} 
    myGraph[6] = [...]bool{false, true, false, true, true, false, false, true} 
    myGraph[7] = [...]bool{false, false, false, false, false, false, true, false} 

    //call dfs by feeding in the source and the destination 
    dfs(1, 7) 
    fmt.Println(paths) 
} 

Output: 
[1 2 5 6 7] 
[1 3 2 5 6 7] 
[1 3 4 6 7] 
[1 3 6 7] 
[1 6 7] 
[[1 6 7 3 2 5] [1 6 7 3 2] [1 6 7 3 2] [1 6 7 3 2 5] [1 6 7 3 2] [1 6 7 3] [1 6 7]] 

ご覧のとおり、スライススライスの最後にはメイン機能が表示されます。ただし、その内容はdfs（）によって出力される個々のスライスとは異なります。

Answer 1

はのは、このコードを少し変更してみましょう：

var myGraph [8][8]bool //the graph 

var visited [8]bool //an array that marks if visited 

var path []int //a slice to store a possible path 

var paths [][]int 

func dfs(src int, dest int) { 
    //add current node to path 
    path = append(path, src) 

    //mark current node as visited 
    visited[src] = true 

    //if the current node is the destination 
    //print the path and return 
    if src == dest { 
     // (A) 
     buffer := make([]int, len(path)) 
     copy(buffer, path) 

     fmt.Println(buffer) 
     paths = append(paths, buffer) //I'm trying to push the path slice into the paths slice 

     // fmt.Println(path) 
     // paths = append(paths, path) //I'm trying to push the path slice into the paths slice 
     return 
    } 

    for i := 1; i <= 7; i++ { //loop through all nodes 

     //if ith node is a neighbour of the current node and it is not visited 
     if myGraph[src][i] && visited[i] == false { 

      // call dfs on the current node 
      dfs(i, dest) 

      //mark the current node as unvisited 
      //so that we can other paths to the final destination 
      visited[i] = false 

      //re-slice the slice - get rid of the current node 
      path = path[:len(path)-1] 
     } 

    } 

} 

func main1() { 
    // path = make([]int, 0, 8) 
    // paths = make([][]int, 0, 10) 

    //creating the graph 
    myGraph[1] = [...]bool{false, false, true, true, false, false, true, false} 
    myGraph[2] = [...]bool{false, true, false, true, false, true, false, false} 
    myGraph[3] = [...]bool{false, true, true, false, true, false, true, false} 
    myGraph[4] = [...]bool{false, false, false, true, false, false, true, false} 
    myGraph[5] = [...]bool{false, false, true, false, false, false, true, false} 
    myGraph[6] = [...]bool{false, true, false, true, true, false, false, true} 
    myGraph[7] = [...]bool{false, false, false, false, false, false, true, false} 

    //call dfs by feeding in the source and the destination 
    dfs(1, 7) 
    fmt.Println(paths) 
} 

そして予想通り、今では動作します！どうして？スライスは参照型であるため、値型ではありません。 pathを後で変更すると、// (A)で行われたようなスナップショットを取らない限り、新しい値が表示されます。